OPTOELECTRONIC SEMICONDUCTOR CHIP AND COMPONENT
20240275125 ยท 2024-08-15
Assignee
Inventors
- Hubert Halbritter (Dietfurt, DE)
- Sven Gerhard (Alteglofsheim, DE)
- Bruno JENTZSCH (Regensburg, DE)
- Tilman R?gheimer (Regensburg, DE)
- Christoph Walter (Regensburg, DE)
Cpc classification
H01S5/18
ELECTRICITY
H01S5/2027
ELECTRICITY
H01S5/185
ELECTRICITY
H01S5/02326
ELECTRICITY
H01S5/02234
ELECTRICITY
International classification
H01S5/185
ELECTRICITY
Abstract
The disclosed optoelectronic semiconductor chip includes a carrier, a semiconductor layer sequence on the carrier having at least one active zone for generating radiation, a layer of high optical refractive index on an output coupling facet of the semiconductor layer sequence for the output coupling of radiation, and a coating of low optical refractive index directly on an outer side of the layer of high optical refractive index for the total internal reflection of the radiation, wherein the semiconductor layer sequence is configured to guide the radiation in the active zone perpendicularly to a growth direction of the semiconductor layer sequence, and the layer of high optical refractive index is configured to deflect the radiation at the outer side parallel to the growth direction.
Claims
1. An optoelectronic semiconductor chip comprising a carrier, a semiconductor layer sequence on the carrier having at least one active zone for generating a radiation, an optical high-refractive index layer on an outcoupling facet of the semiconductor layer sequence for outcoupling the radiation, and an optical low-refractive index coating directly on an outward side of the high-refractive index layer for total reflection of the radiation, wherein the semiconductor layer sequence is configured to guide the radiation in the active zone perpendicularly to a growth direction of the semiconductor layer sequence, and the high-refractive index layer is configured to deflect the radiation at the outward side parallel to the growth direction, the carrier is a substitute carrier and the radiation is emitted away from the carrier due to the outward side, the carrier has a recess for the semiconductor layer sequence so that the carrier has a supporting surface facing the outcoupling facet, and the low-refractive index coating is applied to the supporting surface and the high-refractive index layer is seated on the low-refractive index coating, and the semiconductor layer sequence, seen in plan view and in at least one region without an active zone, is fastened to the low-refractive index coating applied to the carrier by a fastening means.
2. The optoelectronic semiconductor chip according to claim 1, which is a semiconductor laser, wherein at a wavelength of maximum intensity of the radiation the high-refractive index layer has a refractive index of at least 0.6 higher than the low-refractive index layer.
3. The optoelectronic semiconductor chip according to claim 1, wherein a refractive index difference between the active zone and the high-refractive index layer is at most 0.3, wherein the high-refractive index layer is located directly at the outcoupling facet, and the outcoupling facet is oriented transversely to the growth direction.
4. The optoelectronic semiconductor chip according to claim 1, further comprising an outcoupling mirror directly on the outcoupling facet, wherein the high-refractive index layer is located directly on the outcoupling mirror and the outcoupling facet is oriented parallel to the growth direction.
5. The optoelectronic semiconductor chip according to claim 1, wherein the high-refractive index layer is a planarization layer for the outcoupling facet and/or for the outcoupling mirror.
6. The optoelectronic semiconductor chip according to claim 1, wherein the high-refractive index layer is an angle correction layer for the outcoupling facet such that an angle between the outward side and the outcoupling facet is between 0.1? and 20?, inclusive.
7. The optoelectronic semiconductor chip according to claim 1, further comprising a metallization reflective to the radiation and located directly on a side of the low-refractive index coating opposite the outcoupling facet.
8. The optoelectronic semiconductor chip according to claim 1, wherein the low-refractive index coating is perforated at a contact side of the semiconductor layer sequence facing the carrier, so that an electrical contacting means is guided through the low-refractive index coating to the semiconductor layer sequence, wherein at the supporting surface of the carrier the low-refractive index coating is located directly on the carrier.
9. The optoelectronic semiconductor chip according to claim 8, wherein a gap is located at the contact side between the low-refractive index coating and the high-refractive index layer.
10. The optoelectronic semiconductor chip according to claim 9, wherein in a lateral direction, that is, in direction perpendicular to the growth direction and away from the semiconductor layer sequence, a first region of the carrier adjoins the supporting surface and is oriented perpendicular to the growth direction, and a second region of the carrier adjoins the first region, and a thickness of the carrier decreases in the second region in the direction away from the semiconductor layer sequence.
11. The optoelectronic semiconductor chip according to claim 10 wherein the fastening means is based on at least one metal or is a metal alloy.
12. The optoelectronic semiconductor chip according to claim 1, wherein a further facet opposite the outcoupling facet is oriented obliquely with respect to the growth direction, and wherein a further supporting surface associated with the further facet is oriented parallel to the growth direction, so that the further supporting surface is configured to reflect radiation components of the radiation reaching the further supporting surface from the active zone back into the active zone.
13. The optoelectronic semiconductor chip according to claim 1, further comprising an optics for beam correction for the radiation, wherein the optics is located above the exterior surface as seen in plan view.
14. The optoelectronic semiconductor chip according to claim 13, wherein the optics are produced from the carrier.
15. A component comprising a plurality of semiconductor chips according to claim 13, and a mounting platform, wherein the semiconductor chips are mounted on the mounting platform and by means of the optics of the semiconductor chips radiation directions of the semiconductor chips are adapted to each other.
16. An optoelectronic semiconductor chip comprising a carrier, a semiconductor layer sequence on the carrier having at least one active zone for generating a radiation, an optical high-refractive index layer on an outcoupling facet of the semiconductor layer sequence for outcoupling the radiation, and an optical low-refractive index coating directly on an outward side of the high-refractive index layer for total reflection of the radiation, wherein the semiconductor layer sequence is configured to guide the radiation in the active zone perpendicularly to a growth direction of the semiconductor layer sequence, and the high-refractive index layer is configured to deflect the radiation at the outward side parallel to the growth direction.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
In the Figures
[0038]
[0039]
[0040]
[0041]
[0042]
[0043]
[0044]
[0045]
[0046]
[0047]
DETAILED DESCRIPTION
[0048]
[0049] The semiconductor layer sequence 3 has two outcoupling facets 34 oriented approximately 45? to a growth direction G of the semiconductor layer sequence 3. Thereby, the semiconductor layer sequence 3 narrows in the direction away from the growth substrate 21. The radiation generated in the active zone 33 leaves the semiconductor layer sequence 3 through the outcoupling facets 34.
[0050] An optical high-refractive index layer 4 is located directly at each of the outcoupling facets 34. The high-refractive index layer 4 has the same or approximately the same refractive index as the semiconductor layer sequence 3. The high-refractive index layer 4 is, for example, made of NbO or LiNbO and can be applied by means of a sol-gel process, or is made of ZnS or also of sputtered, amorphous GaN. An outward side 45 of the high-refractive index layer 4 is comparatively smooth and may be oriented exactly at a 45? angle relative to the growth direction G. That is, by means of the high-refractive index layer 4, a correction of an orientation of the outcoupling facets 34 and a smoothing of the outcoupling facets 34 can be performed.
[0051] Directly on the outward side 45 is an optically low-refractive index coating 5. The low-refractive index coating 5 is preferably electrically insulating and is, for example, made of SiO.sub.2 or of a fluoride, such as MgF or CaF. The low-refractive index coating 5 may be comparatively thin. In the interaction of the high-refractive index layer 4 and the low-refractive index coating 5, the outward side 45 is configured for total reflection of the radiation R.
[0052] A fastening means 63 is optionally located laterally next to the high-refractive index layer 4. The fastening means 63 is preferably electrically conductive and can be a solder. The fastening means 63 enables electrical contacting and mechanical connection of the semiconductor layer sequence 3 to a substitute carrier 22 as a further carrier 2. The substitute carrier 22 is preferably structured to match the high-refractive index layer 4 and is, for example, made of sapphire. Thus, the active zone 33 is located in or at a recess 24 of the further carrier 2, 22.
[0053] For further electrical contacting of the semiconductor layer sequence 3, the low-refractive index coating 5 can be perforated at a contact side 30 of the semiconductor layer sequence 3 facing the substitute carrier 22, so that an electrical contacting means 64 can pass through the low-refractive index coating 5 to the semiconductor layer sequence 3. At a supporting surface 25 of the substitute carrier 22, the low-refractive index coating 5 is optionally located directly on the substitute carrier 22.
[0054] In the direction away from the semiconductor layer sequence 3, the supporting surface 25 may be followed by a region oriented perpendicular to the growth direction G. The supporting surface 25 may be followed by another region oriented away from the growth substrate 21. This area can optionally be followed by a further area extending away from the growth substrate 21.
[0055] Furthermore, it is optionally possible for a gap 8 to be located on the contact side 30 between the low-refractive index coating 5 and the high-refractive index layer 4.
[0056] Thus, the radiation R generated in the active zone 33 passes through the outcoupling facets 34 into the high-refractive index layer 4 and to the respective outward side 45. At the outward side 45, the radiation R is directed to the growth substrate 21 by means of total reflection and is emitted, for example, from two regions on an emission side 37 of the growth substrate 21.
[0057]
[0058] According to
[0059] In the optional step shown in
[0060] According to
[0061] A tolerance with which an angle of the outcoupling facets 34 of, for example, 45? to the growth direction G in
[0062] In
[0063] In a further process step, not drawn, the components of
[0064] The process of
[0065]
[0066] The end mirror coating 65 may start at the opening for the electrical contact means 64. Alternatively to the illustration in
[0067] In all other respects, the comments on
[0068]
[0069] According to
[0070] In contrast,
[0071] In
[0072] In all other respects, the comments on
[0073] The exemplary embodiments of
[0074] Due to their high power density and narrow radiation emission pattern, GaN-based lasers usually require a hermetically sealed housing to protect an outcoupling facet. This is associated with considerable cost. By coupling out through the carrier 2 and by redirecting the radiation R into the carrier 2, the radiation R is widened in its path, in particular in the case of the semiconductor chips 1 according to
[0075] The outcoupling facet 34 and/or the further facet 36 can be generated by etching as in the preceding embodiments. Furthermore, integrated on-chip TIR deflection mirrors are provided to realize a surface emitter according to the HCSEL concept; TIR stands for total internal reflection. Overall, this means a considerable cost reduction and performance advantages compared to other approaches and solutions, for example, by means of external deflection mirrors or the bonding of prisms or the like.
[0076] According to
[0077] The optical high-refractive index layer 4 is located directly on a side of the outcoupling mirror 61 facing away from the semiconductor layer sequence 3 and is made, for example, of NbO with a refractive index of about 2.44 or of ZnS with a refractive index of about 2.47. The outward side 45 is oriented, for example, at a 45? angle with respect to the growth direction G.
[0078] Directly on the outward side 45 is the optically low-refractive index coating 5, which is, for example, made of SiO.sub.x, MgF or CaF and preferably has a refractive index of at most 2.0. The low-refractive index coating 5 preferably has a constant layer thickness across areas of the outward side 45 that come into contact with the radiation R.
[0079] Optionally, a reflective metallization 62, alternatively a Bragg mirror, is located directly on a side of the low-refractive index coating 5 facing away from the semiconductor layer sequence 3. The reflective metallization 62 is, for example, made of Al, Ag, Au or of a layer system CrAu, depending on the wavelength of the radiation R.
[0080] In order to sufficiently reduce the power density of the radiation R at the emission side 37, the carrier 2 preferably has a thickness of at least 200 ?m and/or of at most 2 mm. For example, the thickness of the carrier 2 is 0.3 mm.
[0081] An effective thickness of the high-refractive index layer 4 in the plane of the active zone 33 and in the direction parallel to the active zone 33 is, for example, at least 2 ?m or at least 8 ?m and/or at most 0.2 mm or at most 0.1 mm or at most 30 ?m. This means that the effective thickness of the high-refractive layer 4 can be significantly smaller than the thickness of the substrate 2.
[0082] For example, a thickness of the low-refractive index coating 5 is at least 0.2 ?m and/or at most 2 ?m.
[0083] The emission side 37 of the carrier 2 is optionally provided with an anti-reflective coating 66, for example, a ?/4 layer of SiO.sub.x or of SiO.sub.xN.sub.y, at least in a region relevant for the radiation R.
[0084] A first electrical contact layer 91 and a second electrical contact layer 92, which are metallic layers, for example, are preferably located on the carrier 2 on the emission side 37 as well as on the contact side 30 of the semiconductor layer sequence 3.
[0085] According to
[0086] Due to the very good refractive index matching of NbO and GaN, no disturbing reflections occur at the corresponding interfaces during the NbO/GaN transition. In addition, NbO as a non-crystalline material can be etched well, for example, to produce the 45? outward side 45.
[0087]
[0088] In all other respects, the comments on
[0089]
[0090] Also illustrated in
[0091] Pulsed GaAs lasers, for example for LiDAR applications and especially triple-stack lasers with three active zones 33 and thus a thick, epitaxially grown semiconductor layer sequence 3, if realized as HCSEL, require an exact 450 slope across the whole semiconductor layer sequence 3, which is difficult to achieve due to the different materials in the active zones 33. If this is not ensured, high losses are incurred, especially for the deeper active zones 33 and the associated waveguides. In particular, it is difficult to precisely hit the 45? slope across the complete thickness of the semiconductor layer sequence 3 if the slope is still part of the resonator.
[0092] Also in the GaAs-based semiconductor chip 1 of
[0093] In the semiconductor chip 1 shown in
[0094] In order to prevent a reflection of the radiation R at the interface between the carrier top side 20 and the high-refractive index layer 4, an anti-reflective coating 66 is preferably present between the carrier 2 and the high-refractive index layer 4. The anti-reflective coating 66 is, for example, a ?/4 layer of TiO.sub.x, in particular if the high-refractive index layer 4 is of SiO.sub.xN.sub.y or of NbO, where the SiO.sub.xN.sub.y may in particular have a refractive index of about 1.75. As an alternative to a single-layer antireflective coating 66, a multilayer system, such as a Bragg layer sequence, can also be used.
[0095] The optics 7 may also include fast axis compensation and/or be configured for angular correction with respect to the 90? deflection of the radiation R. The optics 7 is, for example, glued or bonded or etched into the carrier 2.
[0096] In all other respects, the comments on
[0097]
[0098] In all other respects, the comments on
[0099]
[0100] Furthermore, it is shown in
[0101] In all other respects, the comments on
[0102] In the embodiment shown in
[0103] In all other respects, the comments on
[0104] In
[0105]
[0106] According to
[0107] This etching may include or be a wet chemical and/or a dry chemical process.
[0108] In the step of
[0109] In the step of
[0110]
[0111] At least one metal for the optional reflective metallization 62 is then applied. Unlike shown in
[0112] In the optional step of
[0113] According to
[0114] In the step of
[0115] Finally,
[0116] The process of
[0117] Specifically,
[0118] Due to tolerances in the realization of the outward side 45 in the etching process, there is a slope or skew in the radiation angle, also referred to as tilt. For example, a +/?1? variation in the outward side 45 means a tilt of +/?5? of the emitted radiation R, for example, due to refractive index differences. This is very unfavorable for many applications that require adjustment, collimation and/or focusing of the radiation R.
[0119] By incorporating appropriate lens designs, for example in the GaN substrate 21, these output beam tilts can be compensated for, analogously to a radial LED, for example. In particular, since the laser mode is typically only a few 100 nm to 2 ?m wide at its starting point, but the carrier 2 is much thicker, the beam size at the 45? outward side 45 can be assumed to be a point source for the lens design. The carrier thickness also provides a good definition of the spacing of the lens surface. For example, appropriate radial lens shapes can be realized using etching techniques. Other lens shapes can also be, for example, meta-optical structures or diffractive structures. As a further advantage, compression and/or fast-axis collimation or precollimation can be performed here or integrated into the optical functionality.
[0120] A tilt correction is accordingly illustrated in
[0121] As is also possible in all other exemplary embodiments, the further facet 36 may also be oriented at a 45? angle to the growth direction G. The outcoupling mirror 61 may also be disposed between the carrier 2 and the region of the semiconductor layer sequence 3 with the at least one active zone 33, as is also possible in all other exemplary embodiments.
[0122] In all other respects, the comments on
[0123] According to
[0124] In addition, as is equally possible in all other exemplary embodiments, a luminescent layer 67 may be present on or in place of the anti-reflective coating 66 for wavelength modification of the radiation R.
[0125] In all other respects, the comments on
[0126] In
[0127] In all other respects, the comments on
[0128]
[0129] A semiconductor chip 1 is thus mounted, for example, in an SMD package, which may have contact surfaces on the underside for soldering to a printed circuit board. The package substrate, that is, the mounting platform 11, can be a ceramic, for example, made of AlN, which has electrical vias between its main sides. In addition to the two electrical contacts, a further potential-free contact for heat dissipation can be implemented on a lower side.
[0130] For mechanical protection, the semiconductor chip 1 may be encapsulated in the package, not drawn, for example, with an organic encapsulant, such as an epoxy resin, or with a silicone. If necessary, further optical elements, for example lenses, may be part of the component 10 or the package.
[0131] In all other respects, the comments on
[0132] The housing substrate, that is, the mounting platform 11, can also be a metal leadframe, for example, made of Cu, such as a QFN housing. For this purpose, leadframe parts 14 can be present, which are mechanically connected to each other with a carrier material 13.
[0133] In all other respects, the comments on
[0134] The component 10 according to
[0135] That is, a plurality of the semiconductor chips 1 are assembled and contacted on a common assembly platform 11. The electrical connection of several semiconductor chips 1 is made, for example, as a series circuit. This allows commercially available drivers to be used and reduces the required wire cross-sections. Several electrical strings per mounting platform 11 are possible.
[0136] The common mounting platform 11 may be designed as an SMD package, for example, based on at least one ceramic, as shown in
[0137] For mechanical protection, the semiconductor chips 1 may again be encapsulated, for example, with an organic encapsulant, such as epoxy resin, or with a silicone. Further optical elements, such as lenses, can be part of the structure.
[0138] The component 10 may comprise a suitable component, such as an NTC, for temperature monitoring, not drawn.
[0139] In the case of a printed circuit board as the mounting platform 11, the carrier 13 may have solder pads or a connector for electrical contacting and drill holes for mounting on a heat sink, not shown.
[0140] By means of the optics 7, it is possible in particular to precisely match the radiation directions of the individual semiconductor chips 1 to each other. For this purpose, the optics 7 can optionally be individually adapted to the respective requirements, that is, at semiconductor chip level.
[0141] The components shown in the figures preferably follow one another in the sequence indicated, in particular directly one after the other, unless otherwise described. Components not touching each other in the figures are preferably spaced apart. Insofar as lines are drawn parallel to one another, the associated surfaces are preferably likewise aligned parallel to one another. Furthermore, the relative positions of the drawn components to each other are correctly reproduced in the figures, unless otherwise specified.
[0142] The invention described herein is not limited by the description based on the embodiments. Rather, the invention encompasses any new feature as well as any combination of features, which in particular includes any combination of features in the patent claims, even if this feature or combination itself is not explicitly stated in the patent claims or embodiments.