Optical device structure using GaN substrates and growth structures for laser applications

Abstract

Optical devices having a structured active region configured for selected wavelengths of light emissions are disclosed.

Claims

1. A laser device comprising: a {30-31} crystalline surface region comprising gallium and nitrogen; a laser stripe region formed overlying a portion of the {30-31} crystalline surface region, the laser stripe region being characterized by a cavity orientation parallel to a projection of the c-direction, the laser stripe region having a first end and a second end; a first facet provided on the first end of the laser stripe region; and a second facet provided on the second end of the laser stripe region, wherein the first facet is substantially parallel with the second facet, wherein the {30-31} crystalline surface region is selected from either (30-31) or (30-3-1), and the {30-31} crystalline surface region is off-cut less than +/8 degrees toward or away from an a-plane, wherein the laser device is configured to emit light characterized by a wavelength ranging from about 390 nm to about 420 nm or from about 420 nm to about 440 nm.

2. The laser device of claim 1 wherein the first facet comprises a first mirror surface, the first mirror surface comprising a reflective coating, the reflective coating being selected from silicon dioxide, hafnia, titania, tantalum pentoxide, zirconia, or aluminum oxide.

3. The laser device of claim 1 wherein the first facet and the second facet comprise semipolar surfaces.

4. The laser device of claim 1 wherein a length of the laser stripe region ranges from about 50 microns to about 3000 microns.

5. The laser device of claim 1 further comprising an n-type metal region overlying a backside of the {30-31} crystalline surface region and a p-type metal region overlying an upper portion of the laser stripe region.

6. The laser device of claim 1 wherein the laser stripe region comprises an overlying dielectric layer exposing an upper portion of the laser stripe region.

7. The laser device of claim 1 further comprising an n-type gallium and nitrogen containing cladding region overlying the {30-31} crystalline surface region, and an active region overlying the n-type gallium and nitrogen containing cladding region, wherein the laser stripe region-overlies the active region.

8. The laser device of claim 7 wherein the active region comprises an electron blocking region.

9. The laser device of claim 7 wherein the active region comprises one or more quantum wells and a separate confinement heterostructure disposed between the one or more quantum wells and the n-type gallium and nitrogen containing cladding region.

10. The laser device of claim 1 wherein the {30-31} crystalline surface region is provided on a substrate.

11. A laser device comprising: a {30-31} crystalline surface region comprising gallium and nitrogen, the {30-31} crystalline surface region being selected from either (30-31) or (30-3-1); an active region overlying a portion of the {30-31} crystalline surface region; a laser stripe region formed overlying the active region, the laser stripe region being characterized by a cavity orientation parallel to a projection of the c-direction, the laser stripe region having a first end and a second end; a first facet provided on the first end of the laser stripe region, the first facet being substantially orthogonal to the laser stripe region; and a second facet provided on the second end of the laser stripe, the second facet being substantially orthogonal to the laser stripe region, wherein the {30-31} crystalline surface region is off-cut less than +/3 degrees toward or away from a c-plane, wherein the active region is configured to emit light characterized by a wavelength ranging from about 390 nm to about 420 nm or from about 420 nm to about 440 nm.

12. The laser device of claim 11 wherein each of the first facet and the second facet is sufficiently smooth such that each of the first facet and the second facet acts as a mirror surface.

13. The laser device of claim 11 wherein the first facet and the second facet are cleaved facets.

14. The laser device of claim 11 wherein the {30-31} crystalline surface region is provided on a substrate.

15. A method for manufacturing a laser device, the method comprising: providing a {30-31} crystalline surface region comprising gallium and nitrogen, wherein the {30-31} crystalline surface region is off-cut less than +/3 degrees toward or away from a c-plane; forming an active region overlying a portion of the {30-31} crystalline surface region, wherein the active region is configured to emit light characterized by a wavelength ranging from about 390 nm to about 420 nm or from about 420 nm to about 440 nm; forming a laser stripe region overlying the active region, the laser stripe region being characterized by a cavity orientation parallel to a projection of the c-direction, the laser stripe region having a first end and a second end; and forming one or more cladding layers that comprise less than about 2% mole fraction of AlN.

16. The method of claim 15 wherein the first end and the second end comprise cleaved facets.

17. The method of claim 15 wherein the {30-31} crystalline surface region is provided on a substrate.

18. The method of claim 15 wherein forming the one or more cladding layers comprises forming a plurality of cladding layers.

19. An optical device comprising: a gallium and nitrogen containing surface region having an m-plane nonpolar crystalline orientation; an n-type gallium and nitrogen containing region overlying the surface region; an active region overlying the n-type gallium and nitrogen containing region; at least one quantum well region configured within the active region; and a laser stripe region overlying a portion of the m-plane nonpolar crystalline orientation surface region, the laser stripe region being characterized by a cavity orientation substantially parallel to the c-direction, the laser stripe region having a first end and a second end, wherein the first end is configured to emit light characterized by a wavelength ranging from about 390 nm to about 420 nm or from about 420 nm to about 440 nm.

20. The optical device of claim 19 wherein the m-plane nonpolar crystalline orientation has a miscut of about 0.8 to about 1.2 degrees towards (0001) and about 0.3 to about 0.3 degrees towards (11-20).

21. The optical device of claim 19 wherein laser stripe region has a length of between about 250 microns and about 3000 microns, and a width of about 0.5 microns and about 50 microns.

22. The optical device of claim 19 wherein the first end of the laser stripe region includes a first cleaved facet and the second end of the laser stripe region includes a second cleaved facet.

23. The optical device of claim 19 wherein the first end of the laser stripe region comprises a first mirror surface having an anti-reflective coating, and the second end of the laser stripe region comprises a second mirror surface having a reflective coating selected from silicon dioxide, hafnia, titania, tantalum pentoxide, zirconia, or aluminum oxide.

24. The optical device of claim 19 further comprising an electron blocking layer overlying the active region.

25. The optical device of claim 19 further comprising an n-side SCH layer overlying the n-type gallium and nitrogen containing region.

26. The optical device of claim 19 further comprising a p-side SCH layer overlying the active region.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1A is a simplified perspective view of a laser device fabricated on a semipolar substrate according to an embodiment of the present invention.

(2) FIG. 1B is a simplified perspective view of a laser device fabricated on a non-polar substrate according to an embodiment of the present invention.

(3) FIG. 2 is a detailed cross-sectional view of a laser device fabricated on a non-polar substrate according to an embodiment of the present invention.

(4) FIG. 3 is a simplified diagram illustrating an epitaxial laser structure according to a preferred embodiment of the present invention.

(5) FIGS. 4 through 6 are simplified diagrams illustrating a laser device for a laser device according to a first embodiment of the present invention.

(6) FIGS. 7 through 8 are simplified diagrams illustrating a laser device for a laser device according to a second embodiment of the present invention.

(7) FIGS. 9 through 10 are simplified diagrams illustrating a laser device for a laser device according to a third embodiment of the present invention.

(8) FIGS. 11 through 13 are simplified diagrams illustrating a laser device for a laser device according to a fourth embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(9) According to the present invention, techniques related generally to optical devices are provided. More particularly, the present invention provides a method and device for emitting electromagnetic radiation using semipolar or non-polar gallium containing substrates such as GaN, MN, InN, InGaN, AlGaN, and AlInGaN, and others. Merely by way of example the invention can be applied to the non-polar m-plane or to the semipolar (11-22), (30-31), (30-3-1), (20-21), (20-2-1), (30-32), or (30-3-2), or offcuts thereof. Merely by way of example, the invention can be applied to optical devices, lasers, light emitting diodes, solar cells, photoelectrochemical water splitting and hydrogen generation, photodetectors, integrated circuits, and transistors, among other devices. In a specific embodiment, the present laser device can be employed in either a semipolar or non-polar gallium containing substrate, as described below. Laser diodes according to this invention can offer improved efficiency, cost, temperature sensitivity, and ruggedness over lasers based on SHG technology. Moreover, laser diodes according to this invention can provide an output with a spectral linewidth of 0.5 to 2 nm, which is advantageous in display applications where speckle must be considered.

(10) FIG. 1A is a simplified perspective view of a laser device 100 fabricated on a semipolar substrate according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. One of ordinary skill in the art would recognize other variations, modifications, and alternatives. As shown, the optical device includes a gallium nitride substrate member 101 having a semipolar or non-polar crystalline surface region. In a specific embodiment, the gallium nitride substrate member is a bulk GaN substrate characterized by having a semipolar or non-polar crystalline surface region, but can be others. In a specific embodiment, the bulk nitride GaN substrate comprises nitrogen and has a surface dislocation density below 10.sup.7 cm.sup.2 or 10.sup.5 cm.sup.2. The nitride crystal or wafer may comprise Al.sub.xIn.sub.yGa.sub.1-x-yN, where 0x, y, x+y1. In one specific embodiment, the nitride crystal comprises GaN. In one or more embodiments, the GaN substrate has threading dislocations, at a concentration between about 10.sup.5 cm.sup.2 and about 10.sup.8 cm.sup.2, in a direction that is substantially orthogonal or oblique with respect to the surface. As a consequence of the orthogonal or oblique orientation of the dislocations, the surface dislocation density is below about 10.sup.7 cm.sup.2 or below about 10.sup.5 cm.sup.2. In a specific embodiment, the device can be fabricated on a slightly off-cut semipolar substrate as described in U.S. application Ser. No. 12/749,466, which claims priority to U.S. Provisional No. 61/164,409 filed on Mar. 28, 2009, commonly assigned, and hereby incorporated by reference herein.

(11) In a specific embodiment on semipolar GaN, the device has a laser stripe region formed overlying a portion of the semi polar crystalline orientation surface region. In a specific semipolar GaN embodiment, the laser stripe region is characterized by a cavity orientation is substantially parallel to the m-direction. In a specific embodiment, the laser strip region has a first end 107 and a second end 109.

(12) In a specific embodiment on nonpolar GaN, the device has a laser stripe region formed overlying a portion of the semi or non-polar crystalline orientation surface region, as illustrated by FIG. 1B. The laser stripe region is characterized by a cavity orientation which is substantially parallel to the c-direction. The laser strip region has a first end and a second end. Typically, the non-polar crystalline orientation is configured on an m-plane, which leads to polarization ratios parallel to the a-direction. In some embodiments, the m-plane is the (10-10) family. Of course, the cavity orientation can also be substantially parallel to the a-direction as well. In the specific nonpolar GaN embodiment having the cavity orientation substantially parallel to the c-direction is further described in Laser Device and Method Using Slightly Miscut Non-Polar GaN Substrates, in the names of Raring, James W. and Pfister, Nick listed as U.S. application Ser. No. 12/759,273, which claims priority to U.S. Provisional Ser. No. 61/168,926 filed on Apr. 13, 2009, commonly assigned, and hereby incorporated by reference for all purposes.

(13) In a preferred semipolar embodiment, the device has a first cleaved semipolar facet provided on the first end of the laser stripe region and a second cleaved semipolar facet provided on the second end of the laser stripe region. The first cleaved semipolar facet is substantially parallel with the second cleaved semipolar facet. In a specific embodiment, the semipolar substrate is configured on a (30-31), (30-3-1), (20-21), (20-2-1), (30-32), (30-3-2) or offcut. The laser waveguide cavity is aligned in the projection of the c-direction. Mirror surfaces are formed on each of the cleaved surfaces. The first cleaved semipolar facet comprises a first mirror surface, typically provided by a scribing and breaking process. The scribing process can use any suitable technique, such as a diamond scribe or laser scribe or combinations. In a specific embodiment, the first mirror surface comprises a reflective coating. The reflective coating is selected from silicon dioxide, hafnia, and titania, tantalum pentoxide, zirconia, aluminum oxide, including combinations, and the like. Depending upon the embodiment, the first mirror surface can be provided by an anti-reflective coating. Of course, there can be other variations, modifications, and alternatives.

(14) Also in a preferred semipolar embodiment, the second cleaved semipolar facet comprises a second mirror surface. The second mirror surface can be provided by a scribing and breaking process. Preferably, the scribing is performed by diamond or laser scribing. In a specific embodiment, the second mirror surface comprises a reflective coating, such as silicon dioxide, hafnia, and titania, tantalum pentoxide, zirconia, aluminum oxide, combinations, and the like. In a specific embodiment, the second mirror surface comprises an anti-reflective coating. Of course, there can be other variations, modifications, and alternatives.

(15) In an alternative preferred semipolar embodiment, the device has a first cleaved m-face facet provided on the first end of the laser stripe region and a second cleaved m-face facet provided on the second end of the laser stripe region. The first cleaved m-facet is substantially parallel with the second cleaved m-facet. In a specific embodiment, the semipolar substrate is configured on (11-22) series of planes, enabling the formation of m-facets for laser cavities oriented in the m-direction. Mirror surfaces are formed on each of the cleaved surfaces. The first cleaved m-facet comprises a first mirror surface, typically provided by a scribing and breaking process. The scribing process can use any suitable technique, such as a diamond scribe or laser scribe or combinations. In a specific embodiment, the first mirror surface comprises a reflective coating. The reflective coating is selected from silicon dioxide, hafnia, and titania, tantalum pentoxide, zirconia, aluminum oxide, including combinations, and the like. Depending upon the embodiment, the first mirror surface can be provided by an anti-reflective coating. Of course, there can be other variations, modifications, and alternatives.

(16) In an embodiment, the device includes a {30-31} crystalline surface region having gallium and nitrogen. A laser stripe region overlies a portion of the {30-31} crystalline surface region. The laser stripe region is characterized by a cavity orientation substantially parallel to a projection of the c-direction. The laser stripe region has a first end and a second end. The first end includes a first facet and the second end includes a second facet. The {30-31} crystalline surface region is off-cut less than +/8 degrees towards a c-plane and/or an a-plane.

(17) In a preferred nonpolar embodiment, the device has a first cleaved c-face facet provided on the first end of the laser stripe region and a second cleaved c-face facet provided on the second end of the laser stripe region. In one or more embodiments, the first cleaved c-facet is substantially parallel with the second cleaved c-facet. In a specific embodiment, the nonpolar substrate is configured on (10-10) series of planes, which enables the formation of c-facets for laser cavities oriented in the c-direction. Mirror surfaces are formed on each of the cleaved surfaces. The first cleaved c-facet comprises a first mirror surface. In a preferred embodiment, the first mirror surface is provided by a scribing and breaking process. The scribing process can use any suitable techniques, such as a diamond scribe or laser scribe or combinations. In a specific embodiment, the first mirror surface comprises a reflective coating. The reflective coating is selected from silicon dioxide, hafnia, and titania, tantalum pentoxide, zirconia, aluminum oxide including combinations, and the like. Depending upon the embodiment, the first mirror surface can also comprise an anti-reflective coating. Of course, there can be other variations, modifications, and alternatives.

(18) Also in a preferred nonpolar embodiment, the second cleaved c-facet comprises a second mirror surface. The second mirror surface can be provided by a scribing and breaking process, for example, diamond or laser scribing or the like. In a specific embodiment, the second mirror surface comprises a reflective coating, such as silicon dioxide, hafnia, and titania, tantalum pentoxide, zirconia, aluminum oxide, combinations, and the like. In a specific embodiment, the second mirror surface comprises an anti-reflective coating. Of course, there can be other variations, modifications, and alternatives.

(19) In a specific embodiment, the laser stripe has a length and width. The length ranges from about 250 microns to about 3000 microns. The strip also has a width ranging from about 0.5 microns to about 50 microns, but can be other dimensions. In a specific embodiment, the width is substantially constant in dimension, although there may be slight variations. The width and length are often formed using a masking and etching process, such as commonly used in the art.

(20) In a specific semipolar embodiment, the device is also characterized by a spontaneously emitted light that is polarized in substantially parallel to the projection of the c-direction. That is, the device performs as a laser or the like. In a preferred embodiment, the spontaneously emitted light is characterized by a polarization ratio of greater than about 0.2 and less than about 1 parallel to the projection of the c-direction. In a preferred embodiment, the spontaneously emitted light is characterized by a wavelength ranging from about 500 to about 580 nanometers to yield a green laser. The spontaneously emitted light is highly polarized and is characterized by a polarization ratio parallel to the projection of the c-direction of greater than 0.4. Of course, there can be other variations, modifications, and alternatives.

(21) In a specific nonpolar embodiment, the device is also characterized by a spontaneously emitted light that is polarized parallel to the a-direction. That is, the device performs as a laser or the like. In a preferred embodiment, the spontaneously emitted light is characterized by a polarization ratio of greater than about 0.1 and less than about 1 parallel to the projection of the c-direction. In a preferred embodiment, the spontaneously emitted light characterized by a wavelength ranging from about 475 to about 540 nanometers to yield a blue-green or green laser and others and the spontaneously emitted light is highly polarized and is characterized by a polarization ratio parallel to the a-direction of greater than 0.5. Of course, there can be other variations, modifications, and alternatives.

(22) FIG. 2 is a detailed cross-sectional view of a laser device 200 fabricated on a non-polar substrate according to one embodiment of the present invention. As shown, the laser device includes gallium nitride substrate 203, which has an underlying n-type metal back contact region 201. The metal back contact region preferably is made of a suitable material such as those noted below.

(23) In a specific embodiment, the device also has an overlying n-type gallium nitride layer 205, an active region 207, and an overlying p-type gallium nitride layer structured as a laser stripe region 209. In a specific embodiment, each of these regions is formed using an epitaxial deposition technique of metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), or other epitaxial growth techniques suitable for GaN growth. In a specific embodiment, the epitaxial layer is a high quality epitaxial layer overlying the n-type gallium nitride layer. In some embodiments the high quality layer is doped, for example, with Si or O to form n-type material, with a dopant concentration between about 10.sup.16 cm.sup.3 and 10.sup.20 cm.sup.3.

(24) In a specific embodiment, an n-type Al.sub.uIn.sub.vGa.sub.1-u-vN layer, where 0u, v, u+v1, is deposited on the substrate. In a specific embodiment, the carrier concentration may lie in the range between about 10.sup.16 cm.sup.3 and 10.sup.20 cm.sup.3. The deposition may be performed using metalorganic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE).

(25) As an example, the bulk GaN substrate is placed on a susceptor in an MOCVD reactor. After closing, evacuating, and back-filling the reactor (or using a load lock configuration) to atmospheric pressure, the susceptor is heated to a temperature between about 800 and about 1100 degrees Celsius in the presence of a nitrogen-containing gas. In one specific embodiment, the susceptor is heated to approximately 1000 degrees Celsius under flowing ammonia. A flow of a gallium-containing metalorganic precursor, such as trimethylgallium (TMG) or triethylgallium (TEG) is initiated, in a carrier gas, at a total rate between approximately 1 and 50 standard cubic centimeters per minute (sccm). The carrier gas may comprise hydrogen, helium, nitrogen, or argon. The ratio of the flow rate of the group V precursor (ammonia) to that of the group III precursor (trimethylgallium, triethylgallium, trimethylindium, trimethylaluminum) during growth is between about 2000 and about 12000. A flow of disilane in a carrier gas, with a total flow rate of between about 0.1 and 10 sccm, is initiated.

(26) In a specific embodiment, the laser stripe region is made of the p-type gallium nitride layer 209. In a specific embodiment, the laser stripe is provided by an etching process selected from dry etching or wet etching. In a preferred embodiment, the etching process is dry, but other processes can be used. As an example, the dry etching process is an inductively coupled process using chlorine bearing species or a reactive ion etching process using similar chemistries. The chlorine bearing species are commonly derived from chlorine gas or the like. The device also has an overlying dielectric region, which exposes 213 contact region. In a specific embodiment, the dielectric region is an oxide such as silicon dioxide or silicon nitride. The contact region is coupled to an overlying metal layer 215. The overlying metal layer is a multilayered structure containing gold and nickel (Ni/Au), gold and palladium (Pd/Au), gold and platinum (Pt/Au), but can be others.

(27) In a specific embodiment, the laser device has active region 207. The active region can include one to twenty quantum well regions according to one or more embodiments. As an example following deposition of the n-type Al.sub.uIn.sub.vGa.sub.1-u-vN layer for a predetermined period of time, so as to achieve a predetermined thickness, an active layer is deposited. The active layer may comprise a single quantum well or a multiple quantum well, with 1-10 quantum wells. The quantum wells may comprise InGaN wells and GaN barrier layers. In other embodiments, the well layers and barrier layers comprise Al.sub.wIn.sub.xGa.sub.1-w-xN and Al.sub.yIn.sub.zGa.sub.1-y-zN, respectively, where 0w, x, y, z, w+x, y+z1, where w<u, y and/or x>v, z so that the bandgap of the well layer(s) is less than that of the barrier layer(s) and the n-type layer. The well layers and barrier layers may each have a thickness between about 1 nm and about 40 nm. In another embodiment, the active layer comprises a double heterostructure, with an InGaN or Al.sub.wIn.sub.xGa.sub.1-w-xN layer about 10 nm to 100 nm thick surrounded by GaN or Al.sub.yIn.sub.zGa.sub.1y-zN layers, where w<u, y and/or x>v, z. The composition and structure of the active layer are chosen to provide light emission at a preselected wavelength. The active layer may be left undoped (or unintentionally doped) or may be doped n-type or p-type.

(28) In a specific embodiment, the active region can also include an electron blocking region, and a separate confinement heterostructure. In some embodiments, an electron blocking layer is preferably deposited. The electron-blocking layer may comprise Al.sub.sIn.sub.tGa.sub.1-s-tN, where 0s, t, s+t1, with a higher bandgap than the active layer, and may be doped p-type. In one specific embodiment, the electron blocking layer comprises AlGaN. In another embodiment, the electron blocking layer comprises an AlGaN/GaN super-lattice structure, comprising alternating layers of AlGaN and GaN, each with a thickness between about 0.2 nm and about 5 nm.

(29) As noted, the p-type gallium nitride structure, which can be a p-type doped Al.sub.qIn.sub.rGa.sub.1-q-rN, where 0q, r, q+r1, layer is deposited above the active layer. The p-type layer may be doped with Mg, to a level between about 10.sup.16 cm.sup.3 and 10.sup.22 cm.sup.3, and may have a thickness between about 5 nm and about 1000 nm. The outermost 1-50 nm of the p-type layer may be doped more heavily than the rest of the layer, so as to enable an improved electrical contact. In a specific embodiment, the laser stripe is provided by a dry etching process, but wet etching may also be used. The device also has an overlying dielectric region, which exposes contact region 213. In a specific embodiment, the dielectric region is an oxide such as silicon dioxide.

(30) In a specific embodiment, the metal contact is made of suitable material. The reflective electrical contact may comprise at least one of silver, gold, aluminum, nickel, platinum, rhodium, palladium, chromium, or the like. The electrical contact may be deposited by thermal evaporation, electron beam evaporation, electroplating, sputtering, or another suitable technique. In a preferred embodiment, the electrical contact serves as a p-type electrode for the optical device. In another embodiment, the electrical contact serves as an n-type electrode for the optical device. Of course, there can be other variations, modifications, and alternatives. Further details of the cleaved facets appear below.

(31) FIG. 3 is a simplified diagram illustrating a laser structure according to a preferred embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. One of ordinary skill in the art would recognize other variations, modifications, and alternatives. In a specific embodiment, the device includes a starting material such as a bulk nonpolar or semipolar GaN substrate, but can be others. In a specific embodiment, the device is configured to achieve emission wavelength ranges of 390 nm to 420 nm, 420 nm to 440 nm, 440 nm to 470 nm, 470 nm to 490 nm, 490 nm to 510 nm, 510 nm to 530 nm, and 530 nm to 550 nm, but can be others.

(32) In a preferred embodiment, the growth structure is configured using between 2 and 4 or 5 and 7 quantum wells positioned between n-type and p-type gallium and nitrogen containing cladding layers such as GaN, AlGaN, or InAlGaN. In a specific embodiment, the n-type cladding layer ranges in thickness from 500 nm to 5000 nm and has an n-type dopant such as Si with a doping level of between 1E18 cm.sup.3 and 3E18 cm.sup.3. In a specific embodiment, the p-type cladding layer ranges in thickness from 300 nm to 1000 nm and has a p-type dopant such as Mg with a doping level of between 1E17 cm.sup.3 and 5E19 cm.sup.3. In a specific embodiment, the Mg doping level is graded such that the concentration would be lower in the region closer to the quantum wells.

(33) In a specific preferred embodiment, the quantum wells have a thickness of between 2.0 nm and 4.0 nm or 4.0 nm and 7.0 nm, but can be others. In a specific embodiment, the quantum wells would be separated by barrier layers with thicknesses between 4 nm and 8 nm or 8 nm and 18 nm. The quantum wells and the barriers together comprise a multiple quantum well (MQW) region.

(34) In a preferred embodiment, the device has barrier layers formed from GaN or InGaN. In a specific embodiment using InGaN, the indium contents range from 1% to 5% (molar percent).

(35) An InGaN separate confinement heterostructure layer (SCH) could be positioned between the n-type cladding and the MQW region according to one or more embodiments. Typically, such separate confinement layer is commonly called the n-side SCH. The n-side SCH layer ranges in thickness from 10 nm to 50 nm or 50 nm to 150 nm and ranges in indium composition from 1% to 8% (mole percent), but can be others. In a specific embodiment, the n-side SCH layer may or may not be doped with an n-type dopant such as Si.

(36) In yet another preferred embodiment, an InGaN separate confinement heterostructure layer (SCH) is positioned between the p-type cladding layer and the MQW region, which is called the p-side SCH. In a specific embodiment, the p-side SCH layer ranges in thickness from 10 nm to 50 nm or 50 nm to 100 nm and ranges in indium composition from 1% to 7% (mole percent), but can be others. The p-side SCH layer may or may not be doped with a p-type dopant such as Mg. In another embodiment, the structure would contain both an n-side SCH and a p-side SCH.

(37) In a specific preferred embodiment, an AlGaN electron blocking layer, with an aluminum content of between 6% and 22% (mole percent), is positioned between the MQW and the p-type cladding layer either within the p-side SCH or between the p-side SCH and the p-type cladding. The AlGaN electron blocking layer ranges in thickness from 10 nm to 30 nm and is doped with a p-type dopant such as Mg from 1E18 cm3 and 1E20 cm3 according to a specific embodiment.

(38) Preferably, a p-contact layer positioned on top of and is formed overlying the p-type cladding layer. The p-contact layer would be comprised of a gallium and nitrogen containing layer such as GaN doped with a p-dopant such as Mg at a level ranging from 1E19 cm.sup.3 to 1E22 cm.sup.3.

(39) Several more detailed embodiments, not intended to limit the scope of the claims, are described below.

(40) In a specific embodiment, the present invention provides a laser device capable of emitting 474 nm and also 485 nm, or 470 nm to 490 nm, or 510 nm to 535 nm wavelength light. The device is provided with one or more of the following elements, as also referenced in FIGS. 4 through 6:

(41) an n-type cladding layer with a thickness from 1000 nm to 5000 nm with Si doping level of 1E17 cm.sup.3 to 3E18 cm.sup.3;

(42) an n-side SCH layer comprised of InGaN with molar fraction of indium of between 1.5% and 6% and thickness from 35 to 125 nm;

(43) a multiple quantum well active region layers comprised of three to five 2.5-5.0 nm InGaN quantum wells separated by six 4.5-5.5 nm GaN barriers;

(44) a p-side SCH layer comprised of InGaN with molar fraction of indium of between 1.5% and 5% and thickness from 15 nm to 85 nm;

(45) an electron blocking layer comprised of AlGaN with molar fraction of aluminum of between 6% and 22% and thickness from 10 nm to 15 nm and doped with Mg;

(46) a p-type cladding layer with a thickness from 300 nm to 1000 nm with Mg doping level of 5E17 cm.sup.3 to 1E19 cm.sup.3; and

(47) a p++-GaN contact layer with a thickness from 20 nm to 55 nm with Mg doping level of 1E20 cm.sup.3 to 1E21 cm.sup.3.

(48) In a specific embodiment, the above laser device is fabricated on a nonpolar oriented surface region. Preferably, the 474 nm configured laser device uses a nonpolar (10-10) substrate with a miscut or off cut of 0.3 to 0.3 degrees towards (0001) and 0.3 to 0.3 degrees towards (11-20). In a specific embodiment, the n-GaN/p-GaN is grown using an N.sub.2 subflow and N.sub.2 carrier gas.

(49) In yet an alternative specific embodiment, the present invention provides a laser device capable of emitting 486 nm wavelength light, among others, in a ridge laser embodiment. The device is provided with one or more of the following elements, as also referenced in FIGS. 8 through 9:

(50) an n-GaN cladding layer with a thickness from 100 nm to 5000 nm with Si doping level of 5E17 cm.sup.3 to 3E18 cm.sup.3;

(51) an n-side SCH layer comprised of InGaN with molar fraction of indium of between 3% and 5% and thickness from 40 to 60 nm;

(52) a multiple quantum well active region layers comprised of seven 4.5-5.5 nm InGaN quantum wells separated by eight 4.5-5.5 nm GaN barriers;

(53) a p-side guide layer comprised of GaN with a thickness from 40 nm to 50 nm;

(54) an electron blocking layer comprised of AlGaN with molar fraction of aluminum of between 15% and 22% and thickness from 10 nm to 15 nm and doped with Mg;

(55) a p-GaN cladding layer with a thickness from 400 nm to 1000 nm with Mg doping level of 5E17 cm.sup.3 to 1E19 cm.sup.3; and

(56) p++-GaN contact layer with a thickness from 20 nm to 40 nm with Mg doping level of 2E19 cm.sup.3 to 1E21 cm.sup.3.

(57) In a specific embodiment, the laser device is fabricated on anon-polar (10-10) oriented surface region (m-plane). In a preferred embodiment, the non-polar substrate has a miscut or off cut of 0.8 to 1.2 degrees towards (0001) and 0.3 to 0.3 degrees towards (11-20). In a specific embodiment, the non-polar oriented surface region has an overlying n-GaN/p-GaN grown with H.sub.2/N.sub.2 subflow and H.sub.2 carrier gas.

(58) In a specific embodiment, the present invention provides an alternative device structure capable of emitting 481 nm light, among others, in a ridge laser embodiment. The device is provided with one or more of the following elements, as also referenced in FIGS. 9 through 10;

(59) an n-GaN cladding layer with a thickness from 100 nm to 3000 nm with Si doping level of 5E17 cm.sup.3 to 3E18 cm.sup.3;

(60) an n-side SCH layer comprised of InGaN with molar fraction of indium of between 3% and 6% and thickness from 45 to 80 nm;

(61) a multiple quantum well active region layers comprised of five 4.5-5.5 nm InGaN quantum wells separated by four 9.5 nm to 10.5 nm InGaN barriers with an indium molar fraction of between 1.5% and 3%;

(62) a p-side guide layer comprised of GaN with molar a thickness from 10 nm to 20 nm;

(63) an electron blocking layer comprised of AlGaN with molar fraction of aluminum of between 6% and 22% and thickness from 10 nm to 15 nm and doped with Mg.

(64) a p-GaN cladding layer with a thickness from 400 nm to 1000 nm with Mg doping level of 2E17 cm.sup.3 to 4E19 cm.sup.3; and

(65) a p++-GaN contact layer with a thickness from 20 nm to 40 nm with Mg doping level of 5E19 cm.sup.3 to 1E21 cm.sup.3.

(66) In a specific embodiment, the laser device is fabricated on a non-polar oriented surface region (m-plane). In a preferred embodiment, the non-polar substrate has a miscut or off cut of 0.8 to 1.2 degrees towards (0001) and 0.3 to 0.3 degrees towards (11-20). In a specific embodiment, the non-polar oriented surface region has an overlying n-GaN/p-GaN grown with H.sub.2/N.sub.2 subflow and H.sub.2 carrier gas.

(67) In a specific embodiment, the present invention provides an alternative device structure capable of emitting 501 nm light in a ridge laser embodiment. The device is provided with one or more of the following elements, as also referenced in FIGS. 11 through 13:

(68) an n-GaN cladding layer with a thickness from 100 nm to 3000 nm with Si doping level of 5E17 to 3E18 cm.sup.3;

(69) an n-side SCH layer comprised of InGaN with molar fraction of indium of between 3% and 7% and thickness from 40 to 60 nm;

(70) a multiple quantum well active region layers comprised of seven 3.5-4.5 nm InGaN quantum wells separated by eight 9.5 nm to 10.5 nm GaN barriers;

(71) a p-side SCH layer comprised of InGaN with molar a fraction of indium of between 2% and 5% and a thickness from 15 nm to 25 nm;

(72) an electron blocking layer comprised of AlGaN with molar fraction of aluminum of between 8% and 22% and thickness from 10 nm to 15 nm and doped with Mg;

(73) a p-GaN cladding layer with a thickness from 400 nm to 1000 nm with Mg doping level of 5E17 cm.sup.3 to 1E19 cm.sup.3; and

(74) a p++-GaN contact layer with a thickness from 20 nm to 40 nm with Mg doping level of 1E20 cm.sup.3 to 1E21 cm.sup.3.

(75) In a specific embodiment, the laser device is fabricated on anon-polar (10-10) oriented surface region (m-plane). In a preferred embodiment, the non-polar substrate has a miscut or off cut of 0.8 to 1.2 degrees towards (0001) and 0.3 to 0.3 degrees towards (11-20). In a specific embodiment, the non-polar oriented surface region has an overlying n-GaN/p-GaN grown with H.sub.2/N.sub.2 subflow and H.sub.2 carrier gas. In a preferred embodiment, the laser device configured for a 500 nm laser uses well regions and barriers fabricated using slow growth rates of between 0.3 and 0.6 angstroms per second, but can be others. In a specific embodiment, the slow growth rate is believed to maintain the quality of the InGaN at longer wavelengths.

(76) In a specific embodiment, the present invention includes the following device structure.

(77) An optical device comprising:

(78) a gallium nitride substrate member having a semipolar crystalline surface region, the substrate member having a thickness of less than 500 microns, the gallium and nitride substrate member characterized by a dislocation density of less than 107 cm.sup.2;

(79) a semipolar surface region having a root mean square surface roughness of 10 nm and less over a 5 micron by 5 micron analysis area;

(80) an offcut characterizing the surface region;

(81) a gallium and nitrogen containing n-type cladding layer overlying the surface region, the n-type cladding layer having a thickness from 300 nm to 6000 nm with an n-type doping level of 1E17 cm.sup.3 to 3E18 cm.sup.3;

(82) an n-side separate confining heterostructure (SCH) waveguiding layer overlying the n-type cladding layer, the n-side SCH waveguide layer comprising at least gallium, indium, and nitrogen with a molar fraction of InN of between 1% and 8% and having a thickness from 20 nm to 150 nm;

(83) a multiple quantum well active region overlying the n-side SCH waveguide layer, the multiple quantum well active region comprising two to five 2.0 nm to 4.5 nm InGaN quantum wells separated by 3.5 nm to 20 nm gallium and nitrogen containing barrier layers;

(84) a p-side guide layer overlying the multiple quantum well active region, the p-side guide layer comprising GaN or InGaN with a molar fraction of InN of between 1% and 8% and having a thickness from 10 nm to 120 nm;

(85) a p-type gallium and nitrogen containing cladding layer overlying the multiple quantum well active region, the p-type cladding layer having a thickness from 300 nm to 1000 nm with a p-type doping level of 1E17 cm.sup.3 to 5E19 cm.sup.3;

(86) a p++ gallium and nitrogen containing contact layer overlying the p-type cladding layer, the p++ gallium and nitrogen containing contact layer having a thickness from 10 nm to 120 nm with a p-type doping level of 1E19 cm.sup.3 to 1E22 cm.sup.3;

(87) a waveguide member, the waveguide member being aligned substantially in a projection of the c-direction, the waveguide region comprising a first end and a second end;

(88) a first facet formed on the first end; and

(89) a second facet formed on the second end.

(90) Depending upon the embodiment, the present device structure can be made according to the steps outlined below.

(91) In a specific embodiment, the present invention also includes the following device structure, and its variations in an optical device, and in particular a laser device. In this example, the optical device includes one more of the following elements:

(92) a gallium nitride substrate member having a semipolar crystalline surface region, the substrate member having a thickness of less than 500 microns, the gallium and nitride substrate member characterized by a dislocation density of less than 10.sup.7 cm.sup.2;

(93) a semipolar surface region having an root mean square surface roughness of 10 nm and less over a 5 micron by 5 micron analysis area;

(94) an offcut characterizing the surface region;

(95) a surface reconstruction region configured overlying the semipolar surface region and the n-type cladding layer and at an interface within a vicinity of the semipolar surface region, the surface reconstruction region having an oxygen bearing concentration of greater than 1E17 cm.sup.3;

(96) an n-type cladding layer comprising a first quaternary alloy, the first quaternary alloy comprising an aluminum bearing species, an indium bearing species, a gallium bearing species, and a nitrogen bearing species overlying the surface region, the n-type cladding layer having a thickness from 100 nm to 5000 nm with an n-type doping level of 1E17 cm.sup.3 to 6E18 cm.sup.3;

(97) a first gallium and nitrogen containing epitaxial material comprising a first portion characterized by a first indium concentration, a second portion characterized by a second indium concentration, and a third portion characterized by a third indium concentration overlying the n-type cladding layer;

(98) an n-side separate confining heterostructure (SCH) waveguiding layer overlying the n-type cladding layer, the n-side SCH waveguide layer comprised of InGaN with molar fraction of InN of between 1% and 8% and having a thickness from 30 nm to 150 nm;

(99) a multiple quantum well active region overlying the n-side SCH waveguide layer, the multiple quantum well active region comprising two to five 2.0 nm to 4.5 nm InGaN quantum wells separated by 5 nm to 20 nm gallium and nitrogen containing barrier layers;

(100) a p-side guide layer overlying the multiple quantum well active region, the p-side guide layer comprising GaN or InGaN with a molar fraction of InN of between 1% and 5% and having a thickness from 20 nm to 100 nm;

(101) a second gallium and nitrogen containing material overlying the p-side guide layer;

(102) a p-type cladding layer comprising a second quaternary alloy overlying the second gallium and nitrogen containing material, the p-type cladding layer having a thickness from 300 nm to 1000 nm with a magnesium doping level of 1E17 cm.sup.3 to 4E19 cm.sup.3;

(103) a plurality of hydrogen species, the plurality of hydrogen species spatially disposed within the p-type cladding layer;

(104) a p++ gallium and nitrogen containing contact layer overlying the p-type cladding layer, the p++ gallium and nitrogen containing contact layer having a thickness from 10 nm to 140 nm with a magnesium doping level of 1E19 cm.sup.3 to 1E22 cm.sup.3; and

(105) a waveguide member, the waveguide member being aligned substantially in a projection of the c-direction, the waveguide region comprising a first end and a second end;

(106) a first facet formed on the first end;

(107) a first semipolar characteristic configured on the first facet;

(108) a second facet formed on the second end;

(109) a second semipolar characteristic configured on the second facet;

(110) a first edge region formed on a first side of the waveguide member;

(111) a first etched surface formed on the first edge region;

(112) a second edge region formed on a second side of the waveguide member; and

(113) a second etched surface formed on the second edge region.

(114) In this example, the waveguide member is provided between the first facet and the second facet, e.g., semipolar facets having a scribe region and cleave region. In this example, the scribe region is less than thirty percent of the cleave region to help facilitate a clean break via a skip scribing techniques where the skip is within a vicinity of the ridge. The waveguide member has a length of greater than 300 microns and is configured to emit substantially polarized electromagnetic radiation such that a polarization is substantially orthogonal to the waveguide cavity direction and the polarized electromagnetic radiation having a wavelength of 500 nm and greater and a spontaneous emission spectral full width at half maximum of less than 50 nm in a light emitting diode mode of operation or a spectral line-width of a laser output of greater than 0.4 nm. The wavelength is preferably 520 nm and greater. The wall plug efficiency is 5 percent and greater. Depending upon the embodiment, the present device structure can be made according to the steps outlined below.

(115) In this example, the present method includes providing a gallium nitride substrate member having a semipolar crystalline surface region. The substrate member has a thickness of less than 500 microns, which has been thinned to less than 100 microns by way of a thinning process, e.g., grinding polishing. The gallium and nitride substrate member is characterized by a dislocation density of less than 10.sup.7 cm.sup.2. The semipolar surface region is characterized by an off-set of +/3 degrees from a (20-21) semipolar plane toward a c-plane. As an example, the gallium nitride substrate can be made using bulk growth techniques such as ammonothermal based growth or HVPE growth with extremely high quality seeds to reduce the dislocation density to below 1E5 cm.sup.2, below 1E3 cm.sup.2, or eventually even below 1E1 cm.sup.2.

(116) In this example, the method also includes forming the surface reconstruction region overlying the semipolar surface region. The reconstruction region is formed by heating the substrate in the growth reactor to above 1000 C. with an ammonia (e.g., NH.sub.3) and hydrogen (e.g., H.sub.2) over pressure, e.g., atmospheric. The heating process flattens and removes micro-scratches and other imperfections on the substrate surface that lead to detrimental device performance. The micro-scratches and other imperfections are often caused by substrate preparation, including grinding, lapping, and polishing, among others.

(117) In this example, the present method also forms an n-type cladding layer by introducing gaseous species of at least ammonia with nitrogen or hydrogen and an n-type dopant bearing species. The n-type cladding layer comprises silicon as the n-type dopant. The method also includes forming of the first gallium and nitrogen containing epitaxial material comprises n-type GaN and underlies the n-type quaternary cladding. The cladding layer includes aluminum, indium, gallium, and nitrogen in a wurtzite-crystalline structure. Preferably, the quaternary cladding region facilitates substantial lattice matching to the primary lattice constant of the substrate to achieve an increased aluminum content and a lower index cladding region. The lower index cladding layer enables better confine optical confinement within the active region leading to improved efficiency and gain within the laser device. The cladding layer is made with sufficient thickness to facilitate optical confinement, among other features.

(118) The method includes forming the n-side separate confining heterostructure (SCH) waveguiding layer comprises processing at a deposition rate of less than 1.5 angstroms per second and an oxygen concentration of less than 8E17 cm.sup.3. In this example, the n-side SCH is an InGaN material having a thickness and an oxygen concentration. The oxygen concentration is preferably below a predetermined level within a vicinity of the multiple quantum well regions to prevent any detrimental influences therein. Further details of the multiple quantum well region are provided below.

(119) In this example, the method includes forming the multiple quantum well active region by processing at a deposition rate of less than 1 angstroms per second and an oxygen concentration of less than 8E17 cm.sup.3. The method also includes forming the p-side guide layer overlying the multiple quantum well active region by depositing an InGaN SCH layer with an InN molar fraction of between 1% and 5% and a thickness ranging from 10 nm to 100 nm. The method forms the second gallium and nitrogen-containing material overlying the p-side guide layer by a process comprising a p-type GaN guide layer with a thickness ranging from 50 nm to 300 nm. As an example, the quantum well region can include two to four well regions, among others. Each of the quantum well layers is substantially similar to each other for improved device performance, or may be different.

(120) In this example, the method includes forming an electron blocking layer overlying the p-side guide layer, the electron blocking layer comprising AlGaN with a molar fraction of AlN of between 6% and 22% and having a thickness from 5 nm to 25 nm and doped with a p-type dopant such as magnesium. The method includes forming the p-type cladding layer comprising a hydrogen species that has a concentration that tracks relatively with the p-type dopant concentration. The method includes forming a p++-gallium and nitrogen containing contact layer comprising a GaN material formed with a growth rate of less than 2.5 angstroms per second and characterized by a magnesium concentration of greater than 5E19 cm.sup.3. Preferably, the electron-blocking layer redirects electrons from the active region back into the active region for radiative recombination.

(121) In this example, the present method includes an etching process for forming the waveguide member. The etching process includes using a dry etch technique such as inductively coupled plasma etching or reactive ion etching to etch to a depth that does not penetrate through the quantum well region to maintain the multiple quantum well active region substantially free from damage. In this example, the etching process may be timed or maintained to stop the etching before any damage occurs to the multiple quantum well region. The method includes forming the first facet on the first end and forming the second facet on the second end comprising a scribing and breaking process.

(122) In this example, the present method is generally performed in a MOCVD process. The MOCVD process preferably includes; (1) cleaning (via removal of quartz ware, vacuum, and other cleaning process); (2) subjecting the MOCVD chamber into a plurality of growth species; and (3) removing an impurity to a predetermined level. In this example, the impurity may be an oxygen bearing impurity, among others. In a specific example, the present method is performed using an atmospheric MOCVD tool configured to deposit epitaxial materials at atmospheric pressure, e.g., 700 Torr to 900 Torr.

(123) While the above has been a full description of the specific embodiments, various modifications, alternative constructions and equivalents can be used. Therefore, the above description and illustrations should not be taken as limiting the scope of the present invention which is defined by the appended claims.