Abstract
An optoelectronic component including a waveguide, the waveguide comprising an optically active region (OAR), the OAR having an upper and a lower surface; a lower doped region, wherein the lower doped region is located at and/or adjacent to at least a portion of a lower surface of the OAR, and extends laterally outwards from the OAR in a first direction; an upper doped region, wherein the upper doped region is located at and/or adjacent to at least a portion of an upper surface of the OAR, and extends laterally outwards from the OAR in a second direction; and an intrinsic region located between the lower doped region and the upper doped region.
Claims
1. An optoelectronic component comprising: an optically active region (OAR), including a waveguide ridge, the OAR having an upper surface and a lower surface; a lower doped region, wherein the lower doped region is located at and/or adjacent to at least a portion of the lower surface of the OAR, and extends laterally outwards from the waveguide ridge in a first direction; an upper doped region, wherein a portion of the upper doped region is located at and/or adjacent to at least a portion of the upper surface of the waveguide ridge of the OAR, and the upper doped region extends along a sidewall of the waveguide ridge and laterally outwards from the waveguide ridge in a second direction; and an intrinsic region consisting of an intrinsic material located between the lower doped region and the upper doped region and in direct contact with the lower doped region and the upper doped region, wherein the lower doped region does not directly contact the upper doped region.
2. The optoelectronic component of claim 1, further comprising a first electrode contacting the lower doped region at a first contact surface, and a second electrode contacting the upper doped region at a second contact surface; wherein the first contact surface is laterally offset from the waveguide ridge in the first direction; and wherein the second contact surface is laterally offset from the waveguide ridge in the second direction.
3. The optoelectronic component of claim 2, wherein the first and second contact surfaces are aligned with one another along a lateral plane.
4. The optoelectronic component of claim 2, wherein the upper doped region comprises a first doped zone and a second doped zone; wherein a dopant concentration in the second doped zone of the upper doped region is higher than a dopant concentration in the first doped zone of the upper doped region; and wherein the second doped zone of the upper doped region comprises the second contact surface.
5. The optoelectronic component of claim 4, wherein the first doped zone of the upper doped region is at and/or adjacent to the upper surface of the waveguide ridge of the OAR, and the second doped zone is located at a position which is laterally displaced from the waveguide ridge in the second direction.
6. The optoelectronic component of claim 2, wherein the lower doped region comprises a first doped zone and a second doped zone; wherein a dopant concentration in the second doped zone of the lower doped region is higher than a dopant concentration in the first doped zone of the lower doped region; and wherein the second doped zone of the lower doped region comprises the first contact surface.
7. The optoelectronic component of claim 6, wherein the first doped zone of the lower doped region is located directly underneath the OAR; and the second doped zone of the lower doped region is located within the OAR, laterally displaced from the waveguide ridge, the second doped zone of the lower doped region having an upper surface which comprises the first contact surface, and a lower surface which is in direct contact with the first doped zone of the lower doped region.
8. The optoelectronic component of claim 7, wherein the second doped zone of the lower doped region is located within a portion of the OAR having a reduced height.
9. The optoelectronic component of claim 8, wherein the portion of the OAR having a reduced height is a portion of the OAR which has been etched before a dopant species of the lower doped region is added.
10. The optoelectronic component of claim 6, wherein the first doped zone of the lower doped region is located directly underneath the OAR; the OAR including a slab which extends in the first direction, the slab exhibiting a via through its thickness at a location laterally displaced from the waveguide ridge in the first direction; and wherein the second doped zone of the lower doped region is located within the first doped zone, directly underneath the via.
11. The optoelectronic component of claim 2, wherein the upper doped region, intrinsic region, and lower doped regions form a PIN diode.
12. The optoelectronic component of claim 1, wherein the lower doped region is partially adjacent to the lower surface of the OAR and partially migrated into the OAR at the lower surface.
13. The optoelectronic component of claim 1, wherein the upper doped region is fully located within the OAR.
14. The optoelectronic component of claim 1, wherein the OAR is formed from an electro-absorption material in which the Franz-Keldysh effect occurs in response to application of an applied electric field.
15. The optoelectronic component of claim 1, wherein the OAR is formed from a light absorbing material suitable for generating a current upon detection of light when a voltage bias is applied across the upper and lower doped regions.
16. The optoelectronic component according to claim 1, wherein the optically active region (OAR) includes a waveguide ridge, a first slab on a first side of the waveguide ridge and a second slab on a second side of the of the waveguide ridge, the OAR having an upper surface and a lower surface; wherein the lower doped region is located adjacent to a portion of a lower surface of the OAR; the lower doped region also extending laterally along and adjacent to the first slab of the OAR, away from the waveguide ridge in a first direction; and wherein the upper doped region is located within at least a portion of an upper surface of the waveguide ridge of the OAR, and extends laterally outwards along the second slab of the OAR in a second direction.
17. The optoelectronic component of claim 16, wherein the lower doped region which is located adjacent to a portion of a lower surface of the OAR, migrates into the OAR at the same portion of the lower surface of the OAR.
18. The optoelectronic component of claim 1, further comprising an interface between the optoelectronic component and a first waveguide, wherein the interface is at an angle relative to a guiding direction of the first waveguide which is less than 90.
19. The optoelectronic component of claim 18, wherein the interface is at an angle of between 89 and 80 relative to guiding direction of the first waveguide.
20. The optoelectronic component of claim 18, further comprising a second interface between the optoelectronic component and a second waveguide, wherein the second interface is at an angle relative to a guiding direction of the second waveguide which is less than 90.
21. The optoelectronic component of claim 1, wherein an input waveguide of a first refractive index forms an input interface with the waveguide ridge of the OAR, the waveguide ridge of the OAR having a second refractive index; wherein the angle between the input waveguide and the normal to the input interface corresponds to a given angle of incidence; and wherein the angle between the waveguide ridge of the OAR and the normal to the input interface corresponds to the angle of refraction as calculated by Snell's law using the first refractive index, second refractive index and the given angle of incidence.
22. The optoelectronic component of claim 21, wherein an output waveguide of a third refractive index forms an output interface with the waveguide ridge of the OAR; wherein the angle between the waveguide ridge of the OAR and the normal to the output interface corresponds to a second given angle of incidence; and wherein the angle between the output waveguide and the normal to the output interface corresponds to the angle of refraction as calculated by Snell's law using the second refractive index, third refractive index and the second given angle of incidence.
23. A Mach-Zehnder modulator having a first waveguide arm and a second waveguide arm, the first waveguide arm comprising the optoelectronic component of claim 1.
24. The Mach-Zehnder modulator of claim 23, wherein a first contact surface of the first waveguide arm corresponds to a second contact surface of the second waveguide arm to form a shared central contact surface between the first waveguide arm and the second waveguide arm; and wherein a first electrode of the first waveguide arm corresponds to a second electrode of the second waveguide arm to form a shared central electrode between the first waveguide arm and the second waveguide arm.
25. The Mach-Zehnder modulator of claim 23, wherein the first waveguide arm further comprises an interface between the OAR and a first waveguide, wherein the interface is at an angle relative to a guiding direction of the first waveguide which is less than 90.
26. The Mach-Zehnder modulator of claim 25, wherein the interface is at an angle of between 89 and 80 relative to the guiding direction of the first waveguide.
27. The Mach-Zehnder modulator of claim 25, further comprising a second interface between the OAR and a second waveguide, wherein the second interface is at an angle relative to a guiding direction of the second waveguide which is less than 90.
28. The optoelectronic component of claim 1, formed on a silicon-on-insulator platform having a silicon substrate, an insulator layer on top of the silicon substrate, and a silicon device layer on top of the insulator layer, wherein the lower doped region is a doped portion of the silicon device layer, the portion of the silicon device layer being located adjacent the lower surface of the OAR, and wherein the upper doped region is a doped region of the OAR located at the doped region of the OAR.
29. The optoelectronic component of claim 28, wherein the OAR is SiGe or Ge.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) These and other features and advantages of embodiments of the invention will now be appreciated and understood with reference to the specification, claims and appended drawings wherein:
(2) FIG. 1 shows a top down view of optoelectronic component, also shown is an input waveguide with an input taper waveguide region and an output waveguide with an output waveguide taper region;
(3) FIG. 2 shows a cross-sectional view taken through line B-B shown in FIG. 1 of a first embodiment of an optoelectronic device;
(4) FIG. 3 shows a cross-sectional view taken through line B-B shown in FIG. 1 of a second embodiment of an optoelectronic device;
(5) FIG. 4 shows a cross-sectional view taken through line B-B shown in FIG. 1 of a third embodiment of an optoelectronic device;
(6) FIG. 5 shows a cross-sectional view taken through line B-B shown in FIG. 1 of a fourth embodiment of an optoelectronic device;
(7) FIG. 6 shows a cross-sectional view taken through line B-B shown in FIG. 1 of a fifth embodiment of an optoelectronic device;
(8) FIG. 7 shows a cross-sectional view taken through line B-B shown in FIG. 1 of a variant of the fifth embodiment, where the p and n doping is reversed relative to the embodiment shown in FIG. 6;
(9) FIG. 8 shows a cross-sectional view taken through line A-A shown in FIG. 1, showing an example cross section through the input waveguide;
(10) FIG. 9 shows a cross-sectional view taken through line A-A shown in FIG. 1, the line C-C is also shown in FIGS. 2 and 3;
(11) FIG. 10A shows a cross-sectional view of a sixth embodiment of an optoelectronic device, this embodiment may be formed on a nominally 0.8 um (0.2-1 um) SOI platform;
(12) FIG. 10B shows a cross-sectional view of a seventh embodiment of an optoelectronic device, this embodiment may be formed on a nominally 0.8 um SOI platform;
(13) FIG. 11A shows a cross-sectional view of an eighth embodiment of an optoelectronic device, this embodiment may be formed on a 0.8 um SOI platform;
(14) FIG. 11B shows a cross-sectional view of a ninth embodiment of an optoelectronic device, this embodiment may be formed on a 0.8 um SOI platform;
(15) FIG. 12A shows a cross-sectional view of a 10th embodiment of an optoelectronic device s, this embodiment may be formed on a 0.8 um SOI platform;
(16) FIG. 12B shows a cross-sectional view of an 11th embodiment of an optoelectronic device, this embodiment may be formed on a 0.8 um SOI platform;
(17) FIG. 13A shows a cross-sectional view of a 12th embodiment of an optoelectronic device, this embodiment may be formed on a 0.8 um SOI platform;
(18) FIG. 13B shows a cross-sectional view of a 13th embodiment of an optoelectronic device, this embodiment may be formed on a 0.8 um SOI platform;
(19) FIG. 14A shows a cross-sectional view of a 14th embodiment of an optoelectronic device, this embodiment may be formed on a 3 um SOI platform;
(20) FIG. 14B shows a cross-sectional view of a 15th embodiment of an optoelectronic device, this embodiment may be formed on a 3 um SOI platform;
(21) FIG. 15A shows a cross-sectional view of a 16th embodiment of an optoelectronic device, this embodiment may be formed on a 3 um SOI platform;
(22) FIG. 15B shows a cross-sectional view of a 17th embodiment of an optoelectronic device, this embodiment may be formed on a 3 um SOI platform;
(23) FIG. 16A shows a cross-sectional view of an 18th embodiment of an optoelectronic device, this embodiment may be is formed on a 3 um SOI platform;
(24) FIG. 16B shows a cross-sectional view of a 19th embodiment of an optoelectronic device, this embodiment may be formed on a 3 um SOI platform;
(25) FIG. 17A shows a cross-sectional view of a 20th embodiment of an optoelectronic device, this embodiment may be formed on a 3 um SOI platform;
(26) FIG. 17B shows a cross-sectional view of a 21st embodiment of an optoelectronic device, this embodiment may be formed on a 3 um SOI platform;
(27) FIGS. 18a-18o illustrate steps of a method for forming an optoelectronic component. This method is suitable for forming an optoelectronic component on a 0.8 um SOI platform;
(28) FIGS. 19a-19f illustrate steps of a further method for forming an optoelectronic component. This embodiment is suitable for forming an optoelectronic component on a 0.8 um SOI platform;
(29) FIGS. 20a-20p illustrate steps of a further method for forming an optoelectronic component. This embodiment is suitable for forming an optoelectronic component on a 3 um SOI platform;
(30) FIGS. 21a-21g illustrate steps of a further method for forming an optoelectronic component. This embodiment is suitable for forming an optoelectronic component on a 3 um SOI platform;
(31) FIG. 22 shows an example Si waveguide cross-section (for example, an input or output waveguide) and a SiGe waveguide cross-section (for example, the waveguide of optoelectronic component according to the first aspect of embodiments of the invention) at the point at which the Si waveguide and SiGe waveguide may contact;
(32) FIG. 23 shows a cross-sectional view taken through line B-B shown in FIG. 1 of a further embodiment of an optoelectronic device;
(33) FIG. 24a-n shows a method suitable for fabricating the optoelectronic device of FIG. 23;
(34) FIG. 25 shows a Mach-Zehnder modulator incorporating optoelectronic devices according to embodiments of the present invention. The Mach-Zehnder modulator may be operated as a differential drive;
(35) FIG. 26 shows a Mach-Zehnder modulator incorporating optoelectronic devices according to embodiments of the present invention. The Mach-Zehnder modulator may be operated as a push-pull drive;
(36) FIG. 27 shows a cross-sectional view taken through line B-B shown in FIG. 1 of a further embodiment of an optoelectronic device;
(37) FIG. 28a-o shows method steps suitable for fabricating the optoelectronic device of FIG. 27;
(38) FIG. 29 shows a cross-sectional view taken through line B-B shown in FIG. 1 of a further embodiment of an optoelectronic device on a 3-m SOI platform;
(39) FIG. 30a-q shows method steps suitable for fabricating the optoelectronic device of FIG. 29;
(40) FIG. 31 depicts an embodiment in which the lower doped region migrates upwards into the OAR;
(41) FIG. 32 shows a top down view of optoelectronic component, also shown is an input waveguide with an input taper waveguide region and an output waveguide with an output waveguide taper region;
(42) FIG. 33 shows a top down view of an optoelectronic component, also shown is an input waveguide with an input taper waveguide region and an output waveguide with an output waveguide taper region where a part of the optoelectronic component has a trapezoidal geometry;
(43) FIG. 34 shows a top down view of an optoelectronic component, also shown is an input waveguide with an input taper waveguide region and an output waveguide with an output waveguide taper region where the optoelectronic component has a parallelogramal geometry;
(44) FIG. 35 shows a top down view of an optoelectronic component, also shown is an input waveguide with an input taper waveguide region and an output waveguide with an output waveguide taper region where the optoelectronic component has a rectangular geometry but has been disposed at an angle relative to the input and output waveguides.
(45) FIG. 36 shows a top down view of an optoelectronic component, also shown is an input waveguide and output waveguide which are disposed at angles and to the guiding direction of the OAR;
(46) FIG. 37 shows a top down view of an optoelectronic component, also shown is an input waveguide and output waveguide which are disposed at angles and to the guiding direction of the OAR;
(47) FIG. 38 shows a top down view of an optoelectronic component, also shown is an input waveguide and output waveguide which are disposed at angles and to the guiding direction of the OAR and are arranged such that their guiding directions are parallel; and
(48) FIG. 39 shows a top down view of an optoelectronic component, also shown is an input waveguide and output waveguide which are disposed at angles and to the guiding direction of the OAR and are arranged such that their guiding directions are parallel and the entire component has been rotated by an angle S relative to a global horizontal.
DETAILED DESCRIPTION
(49) The detailed description set forth below in connection with the appended drawings is intended as a description of exemplary embodiments of an optoelectronic component provided in accordance with the present invention and is not intended to represent the only forms in which the present invention may be constructed or utilized. The description sets forth the features of the present invention in connection with the illustrated embodiments. It is to be understood, however, that the same or equivalent functions and structures may be accomplished by different embodiments that are also intended to be encompassed within the spirit and scope of the invention. As denoted elsewhere herein, like element numbers are intended to indicate like elements or features.
(50) FIG. 1 shows an architecture for an optoelectronic device including an optoelectronic component according to claim 1. The optoelectronic component 101 is shown between an input waveguide 102 and the output waveguide 103. An input taper region 104 of the input waveguide 102 and an output taper region 105 of output waveguide are also shown. The input taper region 104 helps to transition the light from the relatively wide input waveguide 102 to the relatively narrow optoelectronic component 101. Similarly, the output taper region 105 helps to transition the light from the relatively narrow optoelectronic component 101 to the relatively wide output waveguide 103. Two cross-sectional lines A-A and B-B are also shown. The cross-section locations are used when illustrating embodiments of the invention.
(51) FIG. 2 shows a cross section through B-B (see FIG. 1). The cross sectional view illustrates the components and regions and the architecture of the optoelectronic component. A central waveguide of optically active material (for example, SiGe) 201 is shown running along the centre of the optoelectronic componentthis core forms an optically active region (OAR). The waveguide 201 has an upper surface 202 and lower surface 203. The upper surface 202 and the lower surface 203 are oppositely directed to each other.
(52) Extending across the lower surface 203 is a lower p-doped region 204. The lower p-doped region 204 extends across the full width of the lower surface 203 of the waveguide (i.e. the waveguide ridge) 201. Extending laterally away from the waveguide 201 is a lower lateral p-doped region 205. It will be noted that there is a continuous path of doping between the lower p-doped region 204 and lower lateral p-doped region 205. The lower lateral p-doped region 205 and lower p-doped region 204 is joined by a connecting p-doped region 206. The connecting p-doped region 206 extends vertically along a side of the waveguide 201. The connecting p-doped region 206, the lower lateral p-doped region 205 and the lower p-doped region 204 form a single contiguous p-doped region.
(53) A lower super-doped region 207 is formed in the lower lateral p-doped region 205. The lower super-doped region 207 is also p-doped. However, the dopant concentration in the lower super-doped region 207 is higher than the dopant concentration in the lower lateral p-doped region 205.
(54) Extending across the upper surface 202 is an upper n-doped region 208. The upper n-doped region 208 extends across the full or partial width of the upper surface 202 of the waveguide 201. Extending laterally from the waveguide 201 is an upper lateral n-doped region 209. It will be noted that there is a continuous path of doping between the upper n-doped region 208 and upper lateral n-doped region 209. The upper lateral n-doped region 209 and upper n-doped region 208 may be joined by a connecting n-doped region 210. The connecting n-doped region 210 extends vertically along a side of the waveguide 201. The connecting n-doped region 210, the upper lateral n-doped region 209 and the upper n-doped region 208 form a single contiguous n-doped region.
(55) An upper super-doped region 211 is formed in the upper lateral n-doped region 209. The upper super-doped region 211 is also n-doped. However, the dopant concentration in the upper super-doped region 211 is higher than the dopant concentration in the upper lateral n-doped region 209.
(56) A first electrode 212 is attached to the lower super-doped region 207. A second electrode 213 is attached to the upper super-doped region 211. When a voltage is applied between the first electrode 212 and the second electrode 213 a corresponding bias is applied between the upper n-doped region 208 and the lower p-doped region 204. This bias forms an electric field through the waveguide 201. The electric field has field lines that are generally vertical through the waveguide. It will be noted that the electric field is generally vertical and the first 212 and second 213 electrodes are offset horizontally from the waveguide 201. In other words, the orientation of the electric field and the offset direction of the electrodes 212, 213 from the waveguide 201 are opposite. It is important to keep the locations that the electrodes contact the doped regions distant from the waveguide.
(57) A protective layer 214 covers the majority of the upper surface of the component. Although, it will be noted that the upper surfaces of the first and second electrodes 212, 213 are not completely covered by the protective layer 214. In the embodiment of FIG. 2, the protective layer 214 may be formed of SiO.sub.2 (silicon dioxide).
(58) FIG. 3 shows a cross section through B-B (see FIG. 1). The cross sectional view illustrates the components and regions and the architecture of the optoelectronic component. The elements shown in FIG. 3 are numbered similarly to those in FIG. 2 (for example, element 211 in FIG. 2 corresponds to element 311 in FIG. 3).
(59) A difference between the embodiment shown in FIG. 2 and the embodiment shown in FIG. 3 is the cross sectional shape of the waveguide 301. It will be noted that the cross-section of the waveguide 301 has a notch 315 formed in top right hand corner. The notch 315 of the embodiment of FIG. 3 is larger than that shown in the embodiment of FIG. 2. The upper doped region extends across and follows the profile of the notch 315.
(60) In the embodiment of FIG. 3, the lower doped region 304 does not extend to cover the full width of the lower surface 306 of the waveguide 301. The lower doped region does, however, extend such that the maximum extent of the lower doped region 304 is level with the lateral extent of the notch 315 into the waveguide 301.
(61) FIG. 4 shows a cross section through B-B (see FIG. 1). The cross sectional view illustrates the components and regions and the architecture of the optoelectronic component. The elements shown in FIG. 4 are numbered similarly to those in FIG. 2 (for example, element 211 in FIG. 2 corresponds to element 411 in FIG. 4).
(62) The first difference between the embodiment shown in FIG. 2 and the embodiment shown in FIG. 4 is the lower p-doped region 404 and the lower lateral p-doped region 405 form a generally planar arrangement. In others words the lower doped region is generally formed in a single plane. Part of that planar doped region partially covers the lower surface 403 of the waveguide 401.
(63) The second difference between the embodiment shown in FIG. 2 and the embodiment shown in FIG. 4 is that the waveguide 401 has a generally rectangular cross section. In other words, the cross sectional shape of the waveguide 401 does not include any notches or cutouts.
(64) FIG. 5 shows a cross section through B-B (see FIG. 1). The cross sectional view illustrates the components and regions and the architecture of the optoelectronic component. The elements shown in FIG. 5 are numbered similarly to those in FIG. 2 (for example, element 211 in FIG. 2 corresponds to element 511 in FIG. 5).
(65) The first difference between the embodiment shown in FIG. 5 and the embodiment shown in FIG. 2 is the lower p-doped region 504 and the lower lateral p-doped region 505 form a generally planar arrangement. In others words the lower doped region is generally formed in a single plane. Part of that planar doped region partially covers the lower surface 503 of the waveguide 501.
(66) The second difference between the embodiment shown in FIG. 2 and the embodiment shown in FIG. 5 is that the waveguide 501 has an inverted-T cross sectional shape. In other words, the cross sectional shape of the waveguide 501 has a relatively wide base with a relatively narrow upward extension from the base. This shape of waveguide 501 can alternatively be thought of as having a notch on each side 516, 517.
(67) FIG. 6 shows a cross section through B-B (see FIG. 1). The cross sectional view illustrates the components and regions and the architecture of the optoelectronic component. A central waveguide of optically active material (for example, SiGe) 601 is shown running along the centre of the optoelectronic componentthis core includes an optically active region (OAR). The waveguide 601 has an upper surface 602 and lower surface 603. The upper surface 602 and the lower surface 603 are oppositely directed to each other.
(68) The waveguide is an inverted-rib type waveguide that has a T-shaped cross section. The waveguide generally has a narrow stem with a wider top. This shape is illustrated in FIGS. 6 & 7.
(69) Extending across the lower surface 603 is a lower p-doped region 604. The lower p-doped region 604 extends across the full width of the lower surface 603 of the waveguide 601. Extending laterally from the waveguide 601 is a lower lateral p-doped region 605. It will be noted that there is a continuous path of doping between the lower p-doped region 604 and lower lateral p-doped region 605. The lower lateral p-doped region 605 and lower p-doped region 604 is joined by a connecting p-doped region 606. The connecting p-doped region 606 extends vertically along a side of the waveguide 601. The connecting p-doped region 606, the lower lateral p-doped region 605 and the lower p-doped region 604 form a single contiguous p-doped region.
(70) A lower super-doped region 607 is formed in the lower lateral p-doped region 605. The lower super-doped region 607 is also p-doped. However, the dopant concentration in the lower super-doped region 607 is higher than the dopant concentration in the lower lateral p-doped region 605.
(71) Extending across the upper surface 602 is an upper n-doped region 608. The upper n-doped region 608 extends across the full width of the upper surface 602 of the waveguide 601. Extending laterally from the waveguide 601 is an upper lateral n-doped region 609. It will be noted that there is a continuous path of doping between the upper n-doped region 608 and upper lateral n-doped region 609. The upper lateral n-doped region 609 and upper n-doped region 608 may be joined by a connecting n-doped region 610. The connecting n-doped region 610 extends vertically along a side of the waveguide 601. The connecting n-doped region 610, the upper lateral n-doped region 609 and the upper n-doped region 608 form a single contiguous n-doped region.
(72) An upper super-doped region 611 is formed in the upper lateral n-doped region 609. The upper super-doped region 611 is also n-doped. However, the dopant concentration in the upper super-doped region 611 is higher than the dopant concentration in the upper lateral n-doped region 609.
(73) FIG. 7 shows an alternative to the embodiment of FIG. 6, wherein the dopant species have been reversed. The lower doped regions are n-doped and the upper doped regions are p-doped in the embodiment shown in FIG. 7, opposite to the embodiment shown in FIG. 6.
(74) FIG. 8 shows a cross-sectional view taken through line A-A shown in FIG. 1, showing an example cross section through the input waveguide 2 from FIG. 1. A central waveguide region 801 is shown. The central waveguide region 801 may then be tapered such there is a transition in waveguide dimension and/or shape between the input waveguide and the waveguide of the optoelectronic device (see FIG. 1). A protective layer 802 of e.g. SiO.sub.2 is also shown covering the uppermost surface of the device.
(75) The waveguide 801 shown in FIG. 8 is also equally applicable as an output waveguide (see FIG. 1).
(76) FIG. 9 shows an input/output waveguide similar to the waveguide shown in FIG. 8. The location of the line C-C is shown on FIG. 9 for comparison to other FIGs that show the line C-C.
(77) FIG. 10A shows a cross section through B-B (see FIG. 1). The cross sectional view illustrates the components and regions and the architecture of the optoelectronic component. The components are numbered as in FIG. 2.
(78) The first difference between the embodiment shown in FIG. 10A and the embodiment shown in FIG. 2 is that the first electrode 1012 extends across the protective layer 1015 in a lateral direction away from the waveguide 1001. This means the source of the bias that is applied to the electrodes (and in turn to the doped regions) can be connected further away from the waveguide 1001. The source of the bias may be electronics. The lateral extension of the electrodes increases the ease of manufacture of the device and the attachment of electronics for connecting to the electrodes 1012, 1013.
(79) The first and second electrodes 1012, 1013 may all be formed from aluminium. The embodiment shown in FIG. 10A is formed on a 0.8 um SOI platform 1002.
(80) FIG. 10B shows an alternative to the embodiment of FIG. 10A, wherein the dopant species have been reversed. The lower doped regions are n-doped and the upper doped regions are p-doped in the embodiment shown in FIG. 10B, opposite to the embodiment shown in FIG. 10A.
(81) FIG. 11A shows a cross section through B-B (see FIG. 1). The cross sectional view illustrates the components and regions and the architecture of the optoelectronic component. The components are numbered as in FIG. 3.
(82) The first difference between the embodiment shown in FIG. 11A and the embodiment shown in FIG. 3 is that the first electrode 1112 extends across the protective layer 1114 in a lateral direction away from the waveguide 1101. This means the source of the bias that is applied to the electrodes (and in turn to the doped regions) can be connected further away from the waveguide 1101. The source of the bias may be electronics. The lateral extension of the electrodes increases the ease of manufacture.
(83) The first and second electrodes 1112, 1113 may be formed from aluminium. The embodiment shown in FIG. 11A may be formed on a 0.8 um SOI platform.
(84) FIG. 11B shows an alternative to the embodiment of FIG. 11A, wherein the dopant species have been reversed. The lower doped regions are n-doped and the upper doped regions are p-doped in the embodiment shown in FIG. 11B, opposite to the embodiment shown in FIG. 11A.
(85) FIG. 12A shows a cross section through B-B (see FIG. 1). The cross sectional view illustrates the components and regions and the architecture of the optoelectronic component.
(86) The first difference between the embodiment shown in FIG. 12A and the embodiment shown in FIG. 4 is that the first electrode 1212 extends across the protective layer 1214 in a lateral direction away from the waveguide 1201. This means the source of the bias that is applied to the electrodes (and in turn to the doped regions) can be connected further away from the waveguide 1201. The source of the bias may be electronics. The lateral extension of the electrodes increases the ease of manufacture.
(87) The first and second electrodes 1212, 1213 may be formed from aluminium. The embodiment shown in FIG. 12A may be formed on a 0.8 um SOI platform 1204.
(88) FIG. 12B shows an alternative to the embodiment of FIG. 12A, wherein the dopant species have been reversed. The lower doped regions are n-doped and the upper doped regions are p-doped in the embodiment shown in FIG. 12B, opposite to the embodiment shown in FIG. 12A.
(89) FIG. 13A shows a cross section through B-B (see FIG. 1). The cross sectional view illustrates the components and regions and the architecture of the optoelectronic component.
(90) The first difference between the embodiment shown in FIG. 13A and the embodiment shown in FIG. 5 is that the first electrode 1312 extends across the protective layer 1314 in a lateral direction away from the waveguide 1301. This means the source of the bias that is applied to the electrodes (and in turn to the doped regions) can be connected further away from the waveguide 1301. The source of the bias may be electronics. The lateral extension of the electrodes increases the ease of manufacture.
(91) The first and second electrodes 1312, 1313 may be formed from aluminium. The embodiment shown in FIG. 13A may be formed on a 0.8 um SOI platform.
(92) FIG. 13B shows an alternative to the embodiment of FIG. 13A, wherein the dopant species have been reversed. The lower doped regions are n-doped and the upper doped regions are p-doped in the embodiment shown in FIG. 13B, opposite to the embodiment shown in FIG. 13A.
(93) FIG. 14A shows a cross section through B-B (see FIG. 1). The cross sectional view illustrates the components and regions and the architecture of the optoelectronic component. The elements shown in FIG. 14A are numbered similarly to those in FIG. 2 (for example, element 211 in FIG. 2 corresponds to element 1411 in FIG. 14A).
(94) The difference between the embodiment shown in FIG. 14A and the embodiment shown in FIGS. 2 and 10A is that the embodiment shown in FIG. 14A is formed on a 3 um SOI platform. The optoelectronic component is sunk into the 3 um SOI platform.
(95) FIG. 14B shows an alternative to the embodiment of FIG. 14A, wherein the dopant species have been reversed. The lower doped regions are n-doped and the upper doped regions are p-doped in the embodiment shown in FIG. 14B, opposite to the embodiment shown in FIG. 14A.
(96) FIG. 15A shows a cross section through B-B (see FIG. 1). The cross sectional view illustrates the components and regions and the architecture of the optoelectronic component. The elements shown in FIG. 15A are numbered similarly to those in FIG. 3 (for example, element 311 in FIG. 3 corresponds to element 1511 in FIG. 15A).
(97) The difference between the embodiment shown in FIG. 15A and the embodiment shown in FIGS. 3 and 11A is that the embodiment shown in FIG. 15A is formed on a 3 um SOI platform. The optoelectronic component is sunk into the 3 um SOI platform.
(98) FIG. 15B shows an alternative to the embodiment of FIG. 15A, wherein the dopant species have been reversed. The lower doped regions are n-doped and the upper doped regions are p-doped in the embodiment shown in FIG. 15B, opposite to the embodiment shown in FIG. 15A.
(99) FIG. 16A shows a cross section through B-B (see FIG. 1). The cross sectional view illustrates the components and regions and the architecture of the optoelectronic component. The elements shown in FIG. 16A are numbered similarly to those in FIG. 4 (for example, element 412 in FIG. 4 corresponds to element 1612 in FIG. 16A).
(100) The difference between the embodiment shown in FIG. 16A and the embodiment shown in FIGS. 4 and 12A is that the embodiment shown in FIG. 16A is formed on a 3 um SOI platform. The optoelectronic component is sunk into the 3 um SOI platform.
(101) FIG. 16B shows an alternative to the embodiment of FIG. 16A, wherein the dopant species have been reversed. The lower doped regions are n-doped and the upper doped regions are p-doped in the embodiment shown in FIG. 16B, opposite to the embodiment shown in FIG. 16A.
(102) FIG. 17A shows a cross section through B-B (see FIG. 1). The cross sectional view illustrates the components and regions and the architecture of the optoelectronic component. The elements shown in FIG. 17A are numbered similarly to those in FIG. 4 (for example, element 512 in FIG. 5 corresponds to element 1712 in FIG. 17A).
(103) The difference between the embodiment shown in FIG. 17A and the embodiment shown in FIGS. 5 and 13A is that the embodiment shown in FIG. 17A is formed on a 3 um SOI platform. The optoelectronic component is sunk into the 3 um SOI platform.
(104) FIG. 17B shows an alternative to the embodiment of FIG. 17A, wherein the dopant species have been reversed. The lower doped regions are n-doped and the upper doped regions are p-doped in the embodiment shown in FIG. 17B, opposite to the embodiment shown in FIG. 17A.
(105) FIGS. 18a to 18o illustrate the steps of a method according to the second aspect of embodiments of the present invention.
(106) FIG. 18a shows a cross section of an SOI platform suitable for use in the method according to the second aspect. An upper silicon layer 1801 is shown overlying a buried oxide (BOX) layer 1802. The BOX layer 1802 overlies a lower silicon layer 1803. The upper silicon layer may be a 0.8 m thick intrinsic SOI layer.
(107) In the substrate shown in FIG. 18a, the upper silicon layer 1801 has a thickness of 0.2-1 um.
(108) FIG. 18b shows a cross section of an SOI platform after a first hard mask 1804 has been applied. A gap formed in the first hard mask 1804 exposes the upper silicon layer 1801. In the exposed region, the upper silicon layer 1801 has been partially etched to form a first channel. The first channel does not extend completely through the upper silicon layer 1801.
(109) FIG. 18c shows a cross section of an SOI platform after a second hard mask 1805 has been applied, to expose portions of the upper silicon layer 1801 that were not exposed by the first hard mask (see FIG. 18b). A second etching step has been performed, thus forming a second channel. The first channel is within the base of the second channel, and the second channel is wider than the first channel. The first channel is located in the base of the second channel.
(110) FIG. 18d shows the cross section of the SOI platform after the application of a first photo-resist (PR) mask 1806. Subsequent to the application of the first PR mask 1806, ions 1806a are implanted with an angle (for example an angle of 45 degrees or around 45 degrees) into a lower doped region 1807 in a first dopant implantation step. The first dopant implantation step dopant species is n-type.
(111) FIG. 18e shows the cross section of the SOI platform after the application of a second PR mask 1808. The second PR mask 1808 exposes a region of the lower doped region 1807. A second dopant implantation step is then performed. The dopant species in the second dopant implantation step is the same as the dopant species in the first dopant implantation step. The second implantation step thereby forms a lower super-doped region 1809. The second dopant implantation step dopant species is n-type.
(112) FIG. 18f shows the cross section of the SOI platform after the application of a third PR mask 1810. The third PR mask 1810 exposes an upper region of the upper silicon layer 1801. Subsequent to the application of the third PR mask 1810, ions are implanted into an upper lateral doped region 1811 in a third dopant implantation step. The third dopant implantation step dopant species is p-type.
(113) FIG. 18g shows the cross section of the SOI platform after the application of a fourth PR mask 1812. The fourth PR mask 1812 exposes a region of the upper lateral doped region 1811. A fourth dopant implantation step is then performed. The dopant species in the fourth dopant implantation step is the same as the dopant species in the third dopant implantation step. The fourth dopant implantation step thereby forms an upper super-doped region 1813. The fourth dopant implantation step dopant species is p-type.
(114) FIG. 18h shows the cross section of the SOI platform after the removal of the fourth PR mask and annealing which may be used with RTA (Rapid Thermal Annealing) at 10501100 C. for 10 seconds.
(115) FIG. 18i shows the cross section of the SOI platform after the epitaxial growth of a SiGe layer 1814. Although the method is described below with respect to SiGe, it is envisaged that other optically suitable materials could also be used.
(116) FIG. 18j shows the cross section of the SOI platform after a planarizing step, wherein the deposited SiGe 1814 is planarized by chemical mechanical planarization (CMP). The SiGe layer is planarized such that the top surface 1815 of the SiGe layer is level with the top surface 1816 of the protective upper most adjacent layer.
(117) FIG. 18k shows two alternatives (1) and (2). The upper part of FIG. 18k shows a hard mask 1817 that extends across a lateral portion of the SiGe layer. The lateral portion of the SiGe that is covered by the hard mask 1817 corresponds to the full width of the channel in the Silicon layer 1801 (see FIG. 18b). The SiGe that remains exposed is then etched away, leaving a SiGe waveguide region 1818 with a rectangular cross sectional shape.
(118) Additionally, as shown in the lower part of FIG. 18k, an alternative hard mask 1819 may be formed on the SiGe layer. When etched, the SiGe waveguide region will have an inverted-T shaped cross sectional shape 1819b.
(119) FIG. 18l shows two alternatives, corresponding to the two alternatives shown in FIG. 18k. In each alternative, a first protective layer 1802 of SiO.sub.2 (silicon dioxide) (20-100 nm) has been formed. In both cases, the first protective layer covers the uppermost surface of the device.
(120) FIG. 18m shows two alternatives, corresponding to the two alternatives shown in FIGS. 18k and 18l.
(121) In the first alternative (shown in the upper part of FIG. 18m), a fifth PR mask 1821 has been formed to expose the region of the device above the SiGe waveguide and the region adjacent to the lateral upper p-doped region 1811. An ion implantation step 1821b with 45 degree angle is then used to implant p-type dopant into the exposed regions. Thus an upper doped region 1822 overlying the SiGe waveguide is formed, and a contiguous doped region is formed between the upper doped region and the upper lateral doped region.
(122) In the second alternative (shown in the lower part of FIG. 18m), a fifth PR mask 1821 has been formed to expose the region of the device above the SiGe waveguide and the region adjacent to the upper p-doped region 1811. An ion implantation step with 45 degree angle is then used to implant p-type dopant into the exposed regions. Thus an upper doped region 1822 overlying the SiGe waveguide is formed, and a contiguous doped region is formed between the upper doped region and the upper lateral doped region.
(123) FIG. 18n shows two alternatives, corresponding to the two alternatives shown 18k, 18l and 18m. In each alternative, a second protective layer 1823 e.g. of SiO.sub.2 (silicon dioxide) has been formed. In both cases, the second protective layer 1823 covers the uppermost surface of the device. The second protective layer 1823 has a greater thickness (around 500 nm) than the first protective layer 1820 (see FIG. 18l).
(124) FIG. 18o shows two alternatives, corresponding to the two alternatives shown 18k, 18l, 18m, and 18n. In each alternative, a first electrode 1824 has been formed to contact the lower super-doped region 1809 on a first lateral side, and; a second electrode 1825 has been formed to contact the upper super-doped region 1813 on a second lateral side. The first electrode 1824 extends laterally away from the SiGe waveguide 1818 in the first lateral direction, and the second electrode 1825 extends laterally away from the SiGe waveguide 1818 in the second lateral direction. In other words, the first and second electrodes 1824, 1825 extend in opposite directions away from the SiGe waveguide 1818.
(125) The first and second electrodes 1824, 1825 may each be formed from aluminium and may be deposited in a metallization step. The first and second electrodes 1824, 1825 can be formed simultaneously in their respective positions, thus such architecture of an optoelectronic device simplifies manufacture of such a device.
(126) FIGS. 19a to 19f illustrate steps of a method according to the second aspect of embodiments of the present invention.
(127) FIG. 19a shows a cross section of an SOI platform suitable for use in the method according to the second aspect. An upper silicon layer 1901 is shown overlying a buried oxide (BOX) layer 1902. The BOX layer 1902 overlies a lower silicon layer 1903.
(128) In the substrate shown in FIG. 19a, the upper silicon layer 1901 may have a thickness of 0.2-1 um.
(129) FIG. 19b shows a cross section of an SOI platform after a hard mask 1904 has been applied. A gap formed in the hard mask 1904 exposes the upper silicon layer 1901. In the exposed region, the upper silicon layer 1901 has been partially etched to form a first cavity. The first cavity does not extend completely through the upper silicon layer 1901.
(130) FIG. 19c shows the cross section of the SOI platform after the application of a first photo-resist (PR) mask 1906. Subsequent to the application of the first PR mask 1906, ions 1906b are implanted into a lower doped region 1909 in a first dopant implantation step. The first dopant implantation step dopant species is n-type. The lower doped region 1909 resulting from the first dopant implantation step is generally flat.
(131) FIG. 19d shows the cross section of the SOI platform after the application of a second PR mask 1908. The second PR mask 1908 exposes a region of the lower doped region 1909. A second dopant implantation step 1908b is then performed. The dopant species in the second dopant implantation step is the same as the dopant species in the first dopant implantation step. The second implantation step thereby forms a lower super-doped region 19011. The second dopant implantation step dopant species is n-type.
(132) FIG. 19e shows the cross section of the SOI platform after the application of a third PR mask 1910. Subsequent to the application of the third PR mask 1910, ions 1910b are implanted into an upper lateral doped region 1905 in a third dopant implantation step. The third dopant implantation step dopant species is p-type.
(133) FIG. 19f shows the cross section of the SOI platform after the application of a fourth PR mask 1912. The fourth PR mask 1912 exposes a region of the upper lateral doped region 1905. A fourth dopant implantation step is then performed. The dopant species in the fourth dopant implantation step is the same as the dopant species in the third dopant implantation step 1912b. The fourth dopant implantation step thereby forms an upper super-doped region 1907. The fourth dopant implantation step dopant species is p-type. The remainder of the manufacturing process is as in previous examples.
(134) FIGS. 20a to 20p illustrate steps of a method according to the second aspect of embodiments of the present invention.
(135) FIG. 20a shows a cross section of an SOI platform suitable for use in the method according to the second aspect. An upper silicon layer 2001 is shown overlying a buried oxide (BOX) layer 2002. The BOX layer 2002 overlies a lower silicon layer 2003.
(136) In the substrate shown in FIG. 20a, the upper silicon layer 2001 may have a thickness of 3 m or substantially 3 m.
(137) The upper part of FIG. 20b shows a cross section view along the length of an embodiment of the present invention. In this view, the light will either pass from left to right or right to left. The view generally illustrates a first mode transition zone 2004 and a second mode transition zone 2005. Between the left and right first and second mode transition zones 2004, 2005 there is an elongated waveguide region 2001b. It is in this elongate waveguide region 2001b that an optoelectronic device according to embodiments of the present invention will be located.
(138) The maximum thickness T.sub.1 of the upper silicon layer 2001a is greater than the maximum thickness T.sub.2 of the waveguide region. For example, the maximum thickness T.sub.1 may be 3 m. The thickness of the upper silicon layer T.sub.2 in the waveguide region 2001b may be 0.7-1 m. Between these two thicknesses, it will be noted that the upper silicon region is stepped.
(139) The lower part of FIG. 20b shows a cross sectional view of waveguide region 2001b through the SOI platform that is perpendicular to the direction of light travel.
(140) FIG. 20c shows a cross section of an SOI platform after a first hard mask 2006 has been applied. An opening formed in the hard mask 2006 exposes the upper silicon layer 2001. In the exposed region, the upper silicon layer 2001 has been partially etched to form a first cavity. The first cavity does not extend completely through the upper silicon layer 2001.
(141) FIG. 20d shows a cross section of an SOI platform in which a second hard mask 2007 has been applied to expose portions of the upper silicon layer 2001 that were not exposed by the first hard mask 2006a (see FIG. 20c). A second etching step has been performed, thus forming a second cavity. The first cavity is within the base of the second cavity, and the second cavity is wider than the first cavity. The first cavity is centrally located in the base of the second cavity. It will be noted that the base of the first cavity is exposed (and therefore etched) during both the first and second etching steps.
(142) FIG. 20e shows the cross section of the SOI platform after the application of a first photo-resist (PR) mask 2008. Subsequent to the application of the first PR mask 2008, ions 2008b are implanted into a lower doped region 2009 in a first dopant implantation step with a tilt angle of 45 degree. The first dopant implantation step dopant species is n-type.
(143) FIG. 20f shows the cross section of the SOI platform after the application of a second PR mask 2010. The second PR mask 2010 exposes a region of the lower doped region 2009. A second dopant implantation step is then performed. The dopant species in the second dopant implantation step is the same as the dopant species in the first dopant implantation step. The second implantation step thereby forms a lower super-doped region 2011. The second dopant implantation step dopant species is n-type.
(144) FIG. 20g shows the cross section of the SOI platform after the application of a third PR mask 2012. The third PR mask 2012 exposes an upper region of the upper silicon layer 2001. Subsequent to the application of the third PR mask 2012, ions 2012b are implanted into an upper lateral doped region 2013 in a third dopant implantation step. The third dopant implantation step dopant species is p-type.
(145) FIG. 20h shows the cross section of the SOI platform after the application of a fourth PR mask 2014. The fourth PR mask 2014 exposes a region of the upper lateral doped region 2013. A fourth dopant implantation step 2014b is then performed. The dopant species in the fourth dopant implantation step is the same as the dopant species in the third dopant implantation step. The fourth dopant implantation step thereby forms an upper super-doped region 2015. The fourth dopant implantation step dopant species is p-type.
(146) FIG. 20i shows the cross section of the SOI platform after the first, second, third, and fourth dopant implantation steps have been completed and the first, second, third and fourth PR masks have been removed, and RTA (rapid thermal annealing), for example at 10501100 C. for 10 seconds performed.
(147) FIG. 20j shows the cross section of the SOI platform after the epitaxial growth of a SiGe layer 2016.
(148) FIG. 20k shows the cross section of the SOI platform after a planarizing step, wherein the deposited SiGe 2016 is planarized by chemical mechanical planarization (CMP). The SiGe layer 2016 is smoothed such that the top surface of the SiGe layer 2017 is level with the uppermost surface 2018 of the protective upper most adjacent layer.
(149) FIG. 20l shows the cross section of the SOI platform after the SiGe layer 2016 has been etched back. The SiGe layer has been etched back such that the SiGe fills the second cavity (see FIG. 20d).
(150) FIG. 20m shows two alternatives labelled (1) and (2). The upper part of FIG. 20m shows a first hard mask 2019 that extends across a lateral portion of the SiGe layer. The lateral portion of the SiGe that is covered by the hard mask 2019 corresponds to the full width of the first channel. The SiGe layer that remained exposed has been etched away, leaving a SiGe waveguide region 2020 with a rectangular cross sectional shape.
(151) Alternatively, as shown in the lower part of FIG. 20m, a second hard mask 2021 may be formed on top of the SiGe waveguide region, but not extend across the full width of the first cavity. In this alternative, when etched, the SiGe waveguide region 2020b has an inverted-T shaped cross sectional shape.
(152) FIG. 20n shows two alternatives, corresponding to the next steps for the two alternatives shown in FIG. 20m. In each alternative, a first protective layer 2022 of SiO.sub.2 (silicon dioxide) has been formed. In both cases, the first protective layer 2022 covers the uppermost surface of the device.
(153) FIG. 20o shows two alternatives, corresponding to the two alternatives shown in FIGS. 20m and 20n.
(154) In the upper part of FIG. 20o, the first alternative is shown. In this FIG, the cross section of the SOI platform after the application of the PR mask 2023 is shown. The PR mask 2023 exposes a region of the waveguide region 2020. A dopant implantation step 2023b is then performed with a tilt angle of 45 degree. The dopant species in the dopant implantation step is the same as the dopant species in the third and fourth dopant implantation steps. The dopant implantation step thereby forms an upper doped region 2024. Thus a doped region overlying the SiGe waveguide is formed, and a contiguous doped region is formed between the upper doped region 2024 and the upper lateral doped region 2013. The dopant implantation step dopant species is p-type. The dopant implantation step includes implanting dopant ions through the first protective layer into an upper region of the waveguide region 2020.
(155) In the lower part of FIG. 20o, the second alternative is shown. In this FIG, the cross section of the SOI platform after the application of a PR mask 2023 is shown. The PR mask 2023 exposes a region of the waveguide region 2020. A dopant implantation step is then performed with a tilt angle of 45 degree. The dopant species in the dopant implantation step is the same as the dopant species in the third and fourth dopant implantation steps. The dopant implantation step thereby forms an upper doped region 2024. Thus a doped region overlying the SiGe waveguide is formed, and a contiguous doped region is formed between the upper doped region 2024 and the upper lateral doped region 2013. The dopant implantation step dopant species is p-type. The dopant implantation step includes implanting dopant ions through the first protective layer into an upper region of the waveguide region 2020.
(156) In both alternatives shown in FIG. 20o, the dopant is implanted into an upper region of the material of the SiGe waveguide region (i.e. the SiGe itself) and RTA, for example at 630 C. for 10 seconds.
(157) FIG. 20p shows two alternatives, corresponding to the two alternatives shown in FIGS. 20m, 20n and 20o. In each alternative, a second protective layer 2026 of SiO.sub.2 (silicon dioxide) has been formed. In both cases, the second protective layer 2026 covers the uppermost surface of the device. The second protective layer 2026 has a greater thickness than the first protective layer (see FIG. 20n).
(158) FIGS. 21a to 21g illustrate steps of a method according to the second set of embodiments of the present invention.
(159) FIG. 21a shows a cross section of an SOI platform suitable for use in the method according to the second aspect. An upper silicon layer 2101 is shown overlying a buried oxide (BOX) layer 2102. The BOX layer 2102 overlies a lower silicon layer 2103. The upper silicon layer 2101 has an initial thickness of 3 um.
(160) The upper part of FIG. 21b shows a cross section view along the length of an embodiment of the present invention. In this view, the light will either pass from left to right or right to left. The view generally illustrates a first mode transition zone 2104 and a second mode transition zone 2105. Between the left and right first and second mode transition zones 2104, 2105 there is an elongate waveguide region 2101b. It is in this elongate waveguide region 2101b that an optoelectronic device according to embodiments of the present invention will be located. The thickness T.sub.2 of the intrinsic overlay (in this case Si) could take a value of 0.8 m, or 0.7 m.
(161) The maximum thickness T.sub.1 of the upper silicon layer 2101 is 3 um. The thickness T.sub.2 of the upper silicon layer 2101 in the waveguide region 2101b is 0.2-1 um. Between these two thicknesses, it will be noted that the upper silicon region 2101 is stepped.
(162) The lower part of FIG. 21b shows a cross sectional view of waveguide region 2101b through the SOI platform that is perpendicular to the direction of light travel.
(163) FIG. 21c shows a cross section of an SOI platform after a first hard mask 2106 has been applied. An opening formed in the hard mask 2106 exposes the upper silicon layer 2101. In the exposed region, the upper silicon layer 2101 has been partially etched to form a first cavity. The first cavity does not extend completely through the upper silicon layer 2101.
(164) FIG. 21d shows the cross section of the SOI platform after the application of photo-resist (PR) mask 2108. Subsequent to the application of the PR mask 2108, ions 2108b are implanted into a lower doped region 2109 in a first dopant implantation step. The first dopant implantation step dopant species is n-type. The lower doped region 2109 resulting from the first dopant implantation step is generally flat.
(165) FIG. 21e shows the cross section of the SOI platform after the application of PR mask 2110. The PR mask 2110 exposes a region of the lower doped region 2109. A second dopant implantation step 2110b is then performed. The dopant species in the second dopant implantation step is the same as the dopant species in the first dopant implantation step. The second implantation step thereby forms a lower super-doped region 2111. The second dopant implantation step dopant species is n-type.
(166) FIG. 21f shows the cross section of the SOI platform after the application of PR mask 2112. Subsequent to the application of the PR mask 2112, ions 2112b are implanted into an upper lateral doped region 2113 in a third dopant implantation step. The third dopant implantation step dopant species is p-type.
(167) FIG. 21g shows the cross section of the SOI platform after the application of PR mask 2114. The PR mask 2114 exposes a region of the upper lateral doped region 2113. A fourth dopant implantation step is then performed. The dopant species in the fourth dopant implantation step is the same as the dopant species in the third dopant implantation step. The fourth dopant implantation step thereby forms an upper super-doped region 2115. The fourth dopant implantation step dopant species is p-type. The remainder of the manufacturing process is as in previous examples.
(168) FIG. 22 illustrates two alternative cross sections through input and/or output waveguides (see FIG. 1).
(169) In the left hand example, the waveguide is formed by the upward extension 2201 of the Si from the wide base 2202. Although the example is described in relation to Si waveguides, it should be understood that the geometry could equally be applied to other suitable waveguide materials. The region in which the light is contained is defined by effective changes in refractive index. In this left hand example, changes in refractive index occur at the upper surface 2204 of the upward extension 2201, and the left 2205 and right 2206 surfaces of the upward extension. Effective changes in refractive index also occur because of the relatively small thickness 2207 of the base 2202 relative to the height of the extension 2201. There is also a change in refractive index at the interface 2208 between the base 2202 and the buried oxide layer 2203.
(170) In the right hand example, the waveguide is formed of SiGe 2209. The changes in refractive index that contain the light occur at the edges of the SiGe region. These changes in refractive index may occur at a SiGe-air or SiGeSi boundary (or indeed a SiGeSiO.sub.2 boundary). Again, this example shows a waveguide formed from SiGe. It is envisaged that other suitable optical materials could be used to form a waveguide of the same geometry.
(171) A further embodiment of an optoelectronic device such as an electro absorption modulator (EAM) or a photodiode is described below in relation to FIG. 23 and FIG. 24a-n. In the embodiment shown in FIGS. 23 and 24a-n, it is the lower doped region which exhibits a multilayer structure. The multilayer structure comprises a first doped zone (i.e. a first layer) 2304 formed from an implanted doped portion of the SOI located directly below the OAR. A second doped zone (i.e. a second layer) is formed by implanting dopants into the OAR itself at a region of the OAR located directly above the first doped zone. The second doped zone 2307 has a dopant concentration greater than that of the first doped zone. The lower surface of the second doped zone forms the interface between the first doped zone 2304 and second doped zone 2307. The upper surface of the second doped zone forms the contact surface for the corresponding electrode 2312.
(172) In the embodiment described in FIGS. 23 and 24a-n, the first doped zone of the lower doped region is p doped, and the second doped zone of the lower doped region is p+ doped (where p+ denotes a p doped region with a greater concentration of p dopants). The upper doped region contains an upper doped region in the form of an n doped region 2309 which comprises: an upper n doped waveguide region extending across the upper surface of the OAR waveguide; a lateral n doped region which extends outwards away from the waveguide; and a connecting n doped region which extends vertically along a side of the waveguide to connect the upper n doped waveguide region with the upper lateral n doped region. The connecting n doped region, the upper lateral n doped region and the upper n doped waveguide region form a single contiguous n doped region. The OAR comprises the waveguide ridge and slab regions at either side of the waveguide so that the OAR has an inverted T-shape cross section (the cross section taken transverse to the longitudinal axis of the waveguide). The p+, n and n+ doped regions are all located within the OAR material, whilst the n region extends along the top and the side of the waveguide ridge as well as the slab, the n+ and p+ regions are only found within the slab sections of the OAR, either side of the waveguide ridge.
(173) An upper super-doped region is formed in the upper lateral n doped region. The upper super-doped region is also n doped. However, the dopant concentration in the upper super-doped region is higher than the dopant concentration in the upper lateral n doped region (denoted as an n+ region).
(174) In other embodiments (not shown) the p and n doped regions are reversed so that the lower doped region contains an n doped zone and n+ doped zone and so that the upper doped region is p doped and p+ doped.
(175) The fabrication of the optoelectronic device of FIG. 23 is described below in relation to the steps depicted in FIGS. 24a-n.
(176) As shown in FIG. 24a, a silicon-on-insulator (SOI) waveguide platform is provided; the platform comprising: an underlying substrate, in this case a silicon substrate, an insulator (BOX) layer, and an intrinsic SOI overlay. In the example, the SOI overlay may have a height (i.e. a thickness) of 0.8 m.
(177) Next, as shown in FIG. 24b, a hard mask of 0.5 um SiO.sub.2 2402 is applied to the top surface of the SOI and the unmasked region(s) etched to form a cavity whose depth is 0.7 um. The cavity is designed to receive a piece of an alternative optical material such a SiGe which will form the optically active region of the optoelectronic component (e.g. a modulation region of a modulator). However, before the cavity is filled, the first zone of the lower doped region, in this case the p doped region, is formed within the SOI layer.
(178) As shown in FIGS. 24c and d, the p doped region can be formed by application of a photoresist 2403 to form a mask and subsequent implantation of the dopant via ion implantation (e.g. boron) in the unmasked region. A protection layer of 20 nm-50 nm SiO.sub.2 will be formed before application of the photoresist. Once the photoresist has been removed, an annealing process is carried out to activate the dopant. An example of suitable annealing parameters are 1050 C.-1100 C. for 10 seconds.
(179) Once annealing has taken place, the SiO.sub.2 protection layer is also removed.
(180) As shown in FIGS. 24e and f, the cavity can then be filled by growing the epi layer 2404 (formed, for example from SiGe or Ge) using standard procedures known in the art. Chemical mechanical planarization (CMP) is used to create a flat upper surface.
(181) A waveguide ridge is etched into the epi layer (FIG. 24g) using a hard mask, before a protective layer of SiO.sub.2 is applied (FIG. 24h). The waveguide ridge may have a width of 1.5 um and a depth of 0.4 um. The protective layer may have a thickness of 20 nm-50 nm.
(182) Using a photoresist applied on top of the protective layer to mask off all but the desired area, ion implantation is carried out to create the upper doped region (in this case the n doped region). In the embodiment shown in FIGS. 24i and j, the connecting n doped region, the upper lateral n doped region and the upper n doped waveguide region are formed in a single implantation step.
(183) Also in the embodiment shown in FIG. 24i, an implantation angle of 45 degrees is chosen for the implantation 2407 of dopants. In this way, the doping of the top surface and the sidewall of the ridge waveguide can be carried out in a single step.
(184) Once the first zone 2309 of the upper doped region has been implanted to create an n doped region 2309, a further photoresist layer 2408 is applied, the further photoresist leaving a subsection of the n doped region exposed. This subsection is then implanted with further ions (e.g. phosphorus) in a further ion implantation step to create the second zone of the upper doped region; an n+ doped region within the slab of the OAR. This implantation step may be carried out vertically as shown in FIG. 24j.
(185) Next, a further photoresist 2410 is applied and ion implantation 2411 carried out to form a p+ doped region in the slab of the OAR (SiGe, in this example), at the opposite side of the waveguide from the n+ doped region. The p+ doped region is located directly above the p doped region and extends the entire way through the height of the slab forming a p/p+ interface with the p doped SOI at its lower surface and a contact surface for contact with the electrode 2312 at its upper surface.
(186) An annealing step is then carried out (FIG. 24l) to activate the dopants. Suitable annealing parameters may be at 630 C. for 10 seconds.
(187) As shown in FIG. 24m, a passivation step is carried out by depositing a cladding layer of 0.5 m SiO.sub.2 onto the top surface of the waveguide platform.
(188) Open vias are created using standard techniques (e.g. etching) and a metallization step carried out to create electrodes either side of the waveguide ridge. In the embodiment shown, the electrodes are positioned equidistant from the respective side walls of the waveguide ridge. The electrodes may be formed from aluminium with a thickness of 1 um.
(189) In some embodiments, the p doped region extends at least half way along the width of the OAR so that it is positioned underneath at least half of the waveguide ridge. The extent to which the p doped region extends along the OAR depends upon the diffusion length of the p dopant as well as other factors such as alignment tolerance. In one example embodiment, the waveguide ridge has a width of 1.5 m and the p doped region extends underneath 0.9 m of this width.
(190) FIG. 25 shows a cross section of a Mach-Zehnder modulator incorporating optoelectronic devices as described above in relation to FIGS. 23 and 24a-n. The Mach-Zehnder is formed from a waveguide coupler which splits an incoming waveguide into two waveguide arms 2301a, 2301b, each arm containing an optoelectronic device as shown in FIG. 25. A further waveguide coupler then couples the two arms back together. Application of a bias via the electrodes to the PIN junctions of the optoelectronic devices can be used to control the phase of light in the respective arms. By controlling the relative phase, it is possible to control the interference of light when the two arms recombine and therefore the modulation of light outputted.
(191) In the embodiment shown in FIG. 25, each arm contains an optoelectronic device (in this case an electro absorption modulator, EAM) which is separate from the optoelectronic device (in this case the EAM) of the other arm. Each EAM has its own PIN junctions, which are separate from one another. The doped regions are arranged such that the central region between the two arms of the Mach-Zehnder modulator contains the p doped (and p+ doped) region of one arm and the n doped (and n+ doped) region of the other arm. Each waveguide arm also has its own positive electrode 2312a, 2312b (contacting the p+ doped region) and negative electrode 2313a, 2313b (contacting the n+ doped region).
(192) The Mach-Zehnder modulator of FIG. 25 may therefore be operated as a differential drive. Alternatively, if an external connection to connect the two n electrodes or the two p electrodes is made, this would enable the Mach-Zehnder modulator to be operated as a push-pull drive.
(193) FIG. 26 shows an alternative Mach-Zehnder modulator incorporating optoelectronic devices such as those described in relation to FIGS. 23 and 24a-n. The Mach-Zehnder modulator shown in FIG. 26 differs from that for FIG. 25 in that the two arms share a common electrode. This means that the Mach-Zehnder modulator is operated as a push-pull drive.
(194) In more detail a single doped portion contains both the upper doped portion of the optoelectronic device of a first arm and also the upper doped portion of the optoelectronic device of the second arm. The single doped portion is formed within a single piece of optically active material (OAM), the single OAM including the OARs of both the first arm and second arm.
(195) The single doped portion comprises a first doped zone which includes doped portions at the top and sidewall of each waveguide as well as a lateral portion extending from one waveguide to the other. The single doped portion also includes a second doped zone with a greater dopant concentration than the first doped zone. In the embodiment shown in FIG. 26, the second dopant zone is located midway between the first waveguide arm and the second waveguide arm. The common electrode is located directly above the second dopant zone.
(196) In the embodiment shown in FIG. 26, the shared upper doped portion is an n doped region, and each arm exhibits its own p doped regions located underneath the OAR of that waveguide. However, it is envisaged that the p and n doped regions could be reversed.
(197) A further embodiment of an optoelectronic device such as an EAM or photodiode is described below with reference to FIG. 27 and FIG. 28a-o. This embodiment differs from that of FIG. 23 and FIG. 24a-n in that it the fabrication method includes an extra step of etching a region of the OAR (e.g. SiGe) before that region is implanted to form a p+ doped region. This etching process creates a p+ region of the OAR which has a reduced height as compared to the slab within which it is located.
(198) By etching the slab region of the OAR before p+ doping takes place, it is easier to ensure that the p and p+ doped regions are connected; that is to say that the p+ dopant region (the second zone of the multilayer lower doped portion) reaches through the thickness of the slab from the contact surface at the top surface to the p doped region at the bottom surface. The thickness of the second zone of the multilayer lower doped portion is 0-0.2 um. Where the thickness has a value of 0 um, this should be understood to mean that the p+ dopant region is completely inside of the p region.
(199) The fabrication process can be better understood with reference to FIG. 28a-o.
(200) As shown in FIG. 28a, the starting structure is an upper silicon layer (Silicon on Insulator layer, SOI) 2401 overlying a buried oxide (BOX) layer. The BOX layer overlies a lower silicon layer 2403. In this embodiment, the intrinsic SOI overlay may have a thickness of 0.8 m.
(201) As shown in FIG. 28b, a hard mask 2802 is applied and etch carried out to create a cavity.
(202) Within the cavity, as shown in FIG. 28c: the lower doped region 2304 of the optoelectronic component is created via ion implantation, a photo resist mask 2802b being used to cover all areas other than the desired implantation site. The mask would be deposited on top of a protection layer 2802c (in this case a protection layer of SiO.sub.2, typical thicknesses of which could be 20-50 nm). In this embodiment, the lower doped region is p doped in character, but it is envisaged that this could be reversed (in which case the lower doped region would be n doped). As shown in FIG. 28d an annealing step would be carried out to activate the dopant of the implanted region. Typical parameters for this anneal could be: 1050 C. for 10 sec.
(203) As shown in FIG. 28e, an epitaxial (epi) layer 2804 of an optically active material such as SiGe or Ge is grown within the cavity and then planarized, typically via Chemical-mechanical planarization, CMP (as shown in FIG. 28f).
(204) As shown in FIG. 28g a waveguide 2805 is etched out of the OAM to create the optically active region (OAR) of the device and a protection layer formed. The OAR comprises of a waveguide portion with a slab portion either side. The waveguide and slabs are therefore formed of a single piece of epitaxially grown material such as SiGe or Ge.
(205) A further mask 2805b is applied and a further etch carried out to etch a portion of the slab of the OAR so that a region 2805e of the slab of the OAM has a reduced height. The region of the OAM having the reduced height is located directly above at least a portion of the lower doped region 2304 which was implanted into the SOI itself.
(206) As shown in FIG. 28i, a protective layer 2806a (typically SiO.sub.2 is formed over the entire surface of the device).
(207) As shown in FIG. 28j, a further mask 2806b is applied before ion implantation 2407 of the upper doped region (in this case an n doped region) is carried out. The ion implantation is implantation of the dopant species into the OAM itself and the resulting implanted region extends along the top of the waveguide, the side of the waveguide, and along a lateral portion 2309 extending outwards laterally away from the sidewall of the waveguide. The implantation of these regions is typically carried out in one step, by implanting at an angle to the direction of the sidewall of the waveguide. A suitable angle would be 45 or substantially 45.
(208) As shown in FIG. 28k, a further mask 2806c and implantation step 2807b is carried out to create a second zone of the upper doped region, the second zone having a greater dopant concentration than the first zone. In this case, the greater dopant concentration corresponds to an n+ doped region. This ion implantation is typically carried out at a vertical orientation (i.e. in a direction parallel to the sidewall of the waveguide).
(209) As shown in FIG. 28l, a further implantation step 2807c (implanting a dopant of the opposite type to that deposited in the previous step) may be carried out to generate a second dopant zone of the lower doped region, in this case, a p+ zone within the slab of the OAM. This p+ region is located in the region of the OAM which has been etched to have a reduced height. It therefore lies directly on top of the p doped region implanted within the SOI and is in contact with the p doped area.
(210) The dopant of the second zone of the lower doped region may be activated by annealing, for example at 630 C. for 10 sec (FIG. 28m).
(211) Finally, as shown in FIGS. 28n and 28o, a passivation step is carried out and top cladding 2812 deposited. An open via 2813, 2814 is etched above each of the second zones (i.e. the p+ and n+ doped regions). Respective electrodes 2312, 2313 for contacting the respective second zones are formed by metallization.
(212) A further embodiment of an optoelectronic device such as an EAM or photodiode is described below with reference to FIG. 29 and FIG. 30a-q. This embodiment differs from that of FIG. 27 and FIG. 28a-o in that the starting point is a SOI chip with a SOI overlay which is greater than the height of the waveguide. Initial steps are therefore carried out to create a transition taper from a first height T.sub.1 (i.e. a first, larger, thickness of SOI overlay) to a second height T.sub.2 (i.e. a second, smaller, thickness of SOI overlay). In the embodiments shown the first height T.sub.1 may have a value of 3 m and the second height T.sub.2 may have a value of 0.8 m.
(213) The fabrication process can be better understood with reference to FIG. 30a-q.
(214) As shown in FIG. 30a the fabrication process starts from a platform having a first SOI thickness T.sub.1 (i.e. a first height above the BOX). In the embodiment shown, a typical value would be 3 m, although it is envisaged that other thicknesses would be possible.
(215) As shown in FIG. 30b (which shows a light propagation view) and FIG. 30c (which shows a section view), a transition taper is fabricated from the first height T.sub.1, to the second height T.sub.2 via a stepped region T.sub.3. The embodiments described herein describe a transition with three stepped heights. However, it is envisages that more steps could be added.
(216) The remaining steps are carried out as described in more detail above in relation to FIG. 28. Briefly: FIG. 30d shows the application of hard mask 3002 and etch of SiGe cavity (etch not to scale in figure); and FIG. 30e: shows doping by ion implantation of the lower doped region 3004. In the embodiment described in FIG. 30, this lower doped region corresponds to a p-type doped region. However, it is envisaged that the p and n regions could be swapped.
(217) FIG. 30f shows an annealing step (for example 1050 C., 10 sec) and the removal of the protection layer.
(218) FIGS. 30g and 30h show the growth of an epitaxial layer of an OAM such as SiGe or Ge and then subsequent planarization respectively.
(219) FIG. 30i depicts an additional etching step, not carried out in the embodiment of FIG. 28 in which the epitaxially grown OAM 3044 is etched to a height corresponding to the desired height of the waveguide above the SOI layer.
(220) As shown in FIG. 30j, a waveguide 3005 is etched out of the OAM, once a hard mask 3045 has been applied, the etching being carried out to create the waveguide ridge of the device, and a protection layer formed.
(221) The OAR comprises of a waveguide ridge portion with a slab portion either side. The waveguide and slabs are therefore formed of a single piece of epitaxially grown material 3044 such as SiGe or Ge.
(222) Typically, the waveguide ridge may have a ridge width of 1.5 um and depth 0.4 um.
(223) A further mask 3046 is applied, as shown in FIG. 30k to enable etching of a contact window, the contact window being a region 3047 of the slab of the OAR having a reduced height. The region of the OAM having the reduced height is located directly above at least a portion of the lower doped region 3004 which was implanted into the SOI itself.
(224) In alternative embodiments (not shown), the etching could be continued until a via is formed, passing through the entire slab to the SOI layer underneath. That is to say, a hole would be formed in the slab, exposing the lower doped region underneath.
(225) FIG. 30l: depicts a subsequent step in which a surface protection layer is formed. In some embodiments, this may be a layer of SiO.sub.2, the thickness of which may be 20-50 nm.
(226) FIG. 30m depicts deposition of a photoresist mask 3006b and ion implantation 3007 which provides doping of the upper doped region onto the waveguide ridge of the OAR and also a portion of the adjacent slab of the OAR. This is described in more detail in relation to FIG. 28j above.
(227) As shown in FIG. 30n, a further mask 3006c and implantation step 3007b is carried out to create a second zone of the upper doped region, the second zone having a greater dopant concentration than the first zone. The second doped zone is located within a slab of the OAR, at a location laterally displaced from the waveguide ridge of the OAR. In this case, the greater dopant concentration corresponds to an n+ doped region. This ion implantation is typically carried out at a vertical orientation (i.e. in a direction parallel to the sidewall of the waveguide).
(228) As shown in FIG. 30o, a further resist 3006d and implantation step 3007c (implanting a dopant of the opposite type to that deposited in the previous step) may be carried out to generate a second dopant zone of the lower doped region, in this case, a p+ zone within the slab of the OAM. This p+ region is located in the region of the OAM which has been etched to have a reduced height. It therefore lies directly on top of the p doped region implanted within the SOI and is in contact with the p doped area.
(229) This doping of the second zone of the lower doped region is carried out on a slab of the OAR; the slab at the opposite side of the waveguide ridge to the slab onto which the second zone of the upper doped region was formed.
(230) In the embodiment shown in FIG. 30o, the second zone of the lower doped region corresponds to a p+ doped region, so it may be followed by an annealing process at 630 C. for 10 seconds.
(231) Finally, as shown in FIGS. 30p and 30q, a passivation step is carried out and top cladding 3012 deposited. An open via 3013, 3014 is etched above each of the second zones (i.e. the p+ and n+ doped regions). Respective electrodes 3113, 3114 for contacting the respective second zones are formed by metallization.
(232) A further embodiment of an optoelectronic component is shown in FIG. 31.
(233) This embodiment differs from that of FIG. 29 in that, during the growth of the epitaxial layer and later annealing processes, the dopant of the lower doped region (in this case p doped) diffuses from the bottom of the Si cavity into the OAR. The diffused area 3131 may have a thickness within a range of 10-200 nm. This migrated area caused by the dopant diffusion may reduce the series resistance and, where the device is a modulator, increase the modulator's bandwidth.
(234) This diffusion is shown as an adapted version of the embodiment of FIG. 29. However the additional diffusion step could be applied to any one or more of the embodiments described herein.
(235) Unlike the embodiment shown in FIG. 1, the embodiments discussed in relation to FIGS. 2-31 may be arranged to have angled interfaces (or angled facets) between the OAR and waveguides. In such angled embodiments, the cross-section along B-B would be the same or substantially the same as that shown in FIGS. 2-31, but the device as viewed from above would exhibit angled interfaces. An example of such a further embodiment of an optoelectronic component is shown in FIG. 32.
(236) This embodiment differs from the previous embodiments in that a first interface 3201 and second interface 3202 (or first and second angled facets) of the optoelectronic component 101 are respectively angled relative to a line C-C which is parallel to the direction of light propagation through the device (indicated by the arrows) i.e. it is aligned with the guiding direction of the input waveguide 102 and output waveguide 103. The guiding direction is the direction along which the waveguides transmit light. In this example, the guiding direction of input waveguide 102 is from the left most surface (indicated by the left most arrow) towards the first interface 3201 in a direction generally perpendicular to the plane A-A. The optoelectronic component can be described has having a trapezoidal geometry.
(237) The first interface 3201 is the interface between the input taper region 104 of the input waveguide and the optoelectronic component 101. In comparison to the corresponding interface in, for example, FIG. 1, this first interface is at an angle relative to the guiding direction of the input waveguide. may take values of between 89 and 80, and is in some examples 81. Said another way, the vector of a plane coincident with the interface would be non-parallel with respect to the guiding direction of the input waveguide (whereas, in FIG. 1, the vector would be parallel).
(238) The second interface 3202 is the interface between the output taper region 105 of the output waveguide 103 and the optoelectronic component 101. In comparison to the corresponding interface in, for example, FIG. 1, this second interface is at an angle relative to the direction of light through the device. may take values of between 89 and 80, and is in some cases 81. Said another way, the vector of a plane coincident with the second interface would be non-parallel to the guiding direction of the output waveguide (whereas, in FIG. 1, the vector would be parallel).
(239) The angles and may be equal or may be different. In the example shown in FIG. 32, the angles are equal but have an opposite sense i.e. one is measured clock-wise and the other anti-clockwise such that they are not parallel. The interfaces may be parallel, and in which case they would have the same sense. It may be that only one of the angles has a value which is not equal to 90.
(240) A further embodiment of an optoelectronic component is shown in FIG. 33.
(241) This embodiment differs from the embodiment shown in FIG. 32 in that, whilst a first interface 3201 and second interface 3202 are still angled relative to the line C-C, the entire geometry of the component is not trapezoidal. Instead, the optoelectronic component can be generally discussed as having three regions: a first and second rectangular region 3301 and 3303, and a trapezoidal region 3302 between the first and second rectangular regions. Therefore, the angled interfaces are provided by trapezoidal region 3302 whilst the first and second rectangular regions may provide electrical contacts that may be easier to form. In this embodiment the waveguide interfaces can be provided at non-perpendicular angles with respect to the direction of propagation of light through the device, and can also minimize the portion of the walls of the optically active material interface that are non-parallel to each other, and not parallel to the crystal planes of the Si wafer. This can be helpful because if the cavity within the which the optically active material is grown has non-parallel walls, has walls that are not parallel to the crystal planes of the Si wafer, or has corner that are non-90, the optical or electronic quality of the material could degrade during or after epitaxial growth of the material.
(242) A further embodiment of an optoelectronic component is shown in FIG. 34.
(243) This embodiment differs from the embodiments shown in FIG. 32 and FIG. 33 in that the optoelectronic component has a generally parallelogramal geometry. Therefore the first and second interface 3201 and 3202 are provided by the parallel sides of the parallelogram which intersect the first and second tapered waveguides 104 and 105. In this embodiment the walls of the cavity within the optically active material may be grown to be parallel along their entire lengths whilst still having the waveguide interfaces at non-perpendicular angles with respect to the direction of propagation of light through the device, but the corners of the cavity are not 90, and two sides are not parallel to the crystal planes of the Si wafer.
(244) A further embodiment of an optoelectronic component is shown in FIG. 35.
(245) This embodiment differs from the embodiments shown in FIGS. 32-34 in that the optoelectronic component 101 has a generally rectangular geometry. However, the component 101 is disposed at an angle relative direction C-C. Therefore the two sides of the rectangle which intersect the first and second tapered waveguides provide the first and second interfaces 3201 and 3202. In this embodiment, the walls of the cavity within which the optically active material may be grown to be parallel along their entire lengths, and keep all corners of the cavity at 90, and still have the waveguide interfaces at non-perpendicular angles with respect to the direction of propagation of light through the device, but all four sides are not parallel to the crystal planes of the Si wafer. Alternatively, the cavity walls could be orientated parallel to the Si wafer crystal planes, and instead the waveguides can be angled with respect to the Si wafer crystal planes. In this variant, it may be necessary to rotate the wafer off of the normal angle (parallel to the Si wafer crystal planes) during the diode implantation steps. This can help to ensure that the implantation beam is incident uniformly along the waveguide in the optically active region.
(246) A further embodiment of an optoelectronic component is shown in FIG. 37.
(247) This embodiment differs from embodiments shown previously in that the input waveguide 104 and output waveguide 105 are disposed at respective angles and to the guiding direction of the OAR (the guiding direction of the OAR being parallel to line C-C).
(248) A further embodiment of an optoelectronic is shown in FIG. 37.
(249) This embodiment differs from that shown in FIG. 36 in that it can be described as having generally three regions: a first and second rectangular region 3301 and 3303, and a trapezoidal region 3302 between the first and second rectangular regions. Therefore, the angled interfaces are provided by trapezoidal region 3302 whilst the first and second rectangular regions may provide electrical contacts that may be easier to form. In this embodiment the waveguide interfaces can be provided at non-perpendicular angles with respect to the direction of propagation of light through the device, and can also minimize the portion of the walls of the optically active material interface that are non-parallel to each other, and not parallel to the crystal planes of the Si wafer. This can be helpful because if the cavity within the which the optically active material is grown has non-parallel walls, has walls that are not parallel to the crystal planes of the Si wafer, or has corner that are non-90, the optical or electronic quality of the material could degrade during or after epitaxial growth of the material.
(250) A further embodiment of an optoelectronic component is shown in FIG. 38.
(251) This embodiment differs from the embodiments shown in FIGS. 36 and 37 in that the optoelectronic component has a generally parallelogramal geometry. Therefore, the first and second interfaces 3201 and 3202 are provided by the parallel sides of the parallelogram which intersects the first and second tapered waveguides 104 and 105. In this embodiment, the walls of the cavity within the optically active material may be grown to be parallel along their entire lengths whilst still having the waveguide interfaces at non-perpendicular angles with respect to the direction of the light through the device, but the corners of the cavity are not 90, and the two sides are not parallel to the crystal planes of the Si wafer.
(252) A further embodiment of an optoelectronic component is shown in FIG. 39.
(253) This embodiment differs from the embodiment shown in FIG. 38 in that the optoelectronic component 101 has a generally rectangular geometry. However, the component 101 is disposed at an angle relative to a guiding direction of the OAR (this indicated by the dotted line labeled ). Therefore, the two sides of the rectangle which intersect the first and second tapered waveguides provide the first and second interfaces 3201 and 3202. In this embodiment, the walls of the cavity within which the optically active material may be grown to be parallel along their entire lengths, and keep all corners of the cavity at 90, and still have the waveguide interfaces at non-perpendicular angles with respect to the direction of propagation of light through the device, but all four sides are not parallel to the crystal planes of the Si wafer. Alternatively, the cavity walls could be orientated parallel to the Si wafer crystal planes, and instead the waveguides can be angled with respect to the Si wafer crystal planes. In this variant, it may be necessary to rotate the wafer off the normal angle (parallel to the Si wafer crystal planes) during the diode implantation steps. This can help to ensure that the implantation beam is incident uniformly along the waveguide in the optically active region.
(254) In the embodiments discussed above, the angled interfaces may extend beyond the waveguide. For example, the angled interfaces 3201 and 3202 in FIG. 32 extend beyond a width of the waveguide.
(255) While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.
(256) Embodiments of the invention can be further understood with reference to the disclosures set out in the following numbered paragraphs:
(257) Paragraph 1: An optoelectronic component including a waveguide, the waveguide comprising
(258) an optically active region (OAR), the OAR having an upper and a lower surface;
(259) a lower doped region, wherein the lower doped region is located at and/or adjacent to at least a portion of a lower surface of the OAR, and extends laterally outwards from the OAR in a first direction;
(260) an upper doped region, wherein the upper doped region is located at and/or adjacent to at least a portion of an upper surface of the OAR, and extends laterally outwards from the OAR in a second direction; and
(261) an intrinsic region located between the lower doped region and the upper doped region.
(262) Paragraph 2: An optoelectronic component according to paragraph 1, wherein the doped regions are configured to generate an electric field through the OAR with a field direction, wherein the field direction is different from the first and second directions.
(263) Paragraph 3: An optoelectronic component according to paragraph 2, wherein the field direction is perpendicular to the first and second directions.
(264) Paragraph 4: An optoelectronic component according to paragraph 2, wherein the field direction is angled relative to the first and second directions.
(265) Paragraph 5: An optoelectronic component according to any preceding paragraph, wherein the optically active region is formed from SiGe or Ge.
(266) Paragraph 6: An optoelectronic component according to any preceding paragraph, further comprising a first electrode contacting the lower doped region at a first contact surface, and a second electrode contacting the upper doped region at a second contact surface.
Paragraph 7: An optoelectronic component according to any preceding paragraph, wherein the first contact surface is laterally offset from the waveguide portion in the first direction.
Paragraph 8: An optoelectronic component according to any preceding paragraph, wherein the second contact surface is laterally offset from the OAR in the second direction.
Paragraph 9: An optoelectronic component according to any preceding paragraph, wherein the first and second contact surfaces are equidistant from the OAR.
Paragraph 10: An optoelectronic component according to any preceding paragraph, wherein the first and second contact surfaces are in the same lateral plane.
Paragraph 11: An optoelectronic component according to any preceding paragraph wherein the lower doped region is formed from doped Si.
Paragraph 12: An optoelectronic component according to any preceding paragraph, wherein the upper doped region comprises a first upper zone and a second upper zone.
Paragraph 13: An optoelectronic component according to any one of paragraphs 9-12, wherein the average dopant concentration in the second upper zone is higher than the dopant concentration in the first upper zone.
Paragraph 14: An optoelectronic component according to paragraph 9, wherein first upper zone is at and/or adjacent to the upper surface of the OAR, and second upper zone extends outwards from the OAR in the second direction.
Paragraph 15: An optoelectronic component according to paragraph 9 or 10, wherein the first upper zone is a doped region of the waveguide.
Paragraph 16: An optoelectronic component according to any preceding paragraph, wherein the lower doped region comprises a first lower zone and a second lower zone.
Paragraph 17: An optoelectronic component according to paragraph 13, wherein first lower zone is at and/or adjacent to the lower surface of the OAR, and second lower zone extends outwards from the waveguide portion in the first direction.
Paragraph 18: A method for fabricating an optoelectronic component, comprising:
(267) an etching step, wherein a waveguide trench is etched into an SOI platform;
(268) a lower implantation step, comprising implanting a first dopant species into a base of the trench and on the SOI platform on a first lateral side of the trench, to thereby form a lower doped region;
(269) an upper lateral implantation step, comprising implanting a second dopant species on the SOI platform adjacent the second lateral side of the trench to form a upper lateral doped region;
(270) a waveguide formation step, comprising depositing optically active material into the waveguide trench;
(271) a protection step, comprising forming a protective layer covering the doped regions and the waveguide;
(272) an upper implantation step, comprising implanting the second dopant species into an upper region of the waveguide to form an upper doped region, wherein the upper lateral doped region and the upper doped region are contiguous;
(273) a metallization step, wherein
(274) a first electrode is fabricated, wherein the first electrode contacts the lower doped region at a contact point laterally offset from the waveguide in a first direction;
(275) a second electrode is fabricated, wherein the second electrode contacts the upper lateral doped region at a contact point laterally offset from the waveguide in a second direction.
(276) Paragraph 19: A method according to paragraph 18, wherein the first and second electrodes are fabricated at the same time.
(277) Paragraph 20: A method according to paragraph 18 or paragraph 19, further comprising a secondary lower implantation step, wherein a secondary lateral doped region laterally offset from the waveguide trench is doped with first dopant species to have a higher dopant concentration than the lower doped region.
Paragraph 21: A method according to any one of paragraphs 18-20, further comprising a secondary upper lateral implantation step, wherein a secondary upper lateral doped region laterally offset from the waveguide trench is doped with second dopant species to have a higher dopant concentration than the upper lateral doped region.
Paragraph 22: A method according to any one of paragraphs 18-21, further comprising a waveguide etching step, wherein the deposited optically active material is etched back to form a waveguide.
Paragraph 23: A method according to any one of paragraphs 18-22, further comprising a passivation step, wherein the passivation step comprises the formation of a passivation layer.
