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Opto-electronic and electronic devices using an N-face or M-plane gallium nitride substrate prepared via ammonothermal growth 実績あり

外国特許コード F110003781
整理番号 E06732US2
掲載日 2011年7月4日
出願国 アメリカ合衆国
出願番号 79261510
公報番号 20100275837
公報番号 8263424
出願日 平成22年6月2日(2010.6.2)
公報発行日 平成22年11月4日(2010.11.4)
公報発行日 平成24年9月11日(2012.9.11)
優先権データ
  • 11/765,629 (2007.6.20) US
  • 60/815,507P (2006.6.21) US
発明の名称 (英語) Opto-electronic and electronic devices using an N-face or M-plane gallium nitride substrate prepared via ammonothermal growth 実績あり
発明の概要(英語) A method for growing III-V nitride films having an N-face or M-plane using an ammonothermal growth technique.
The method comprises using an autoclave, heating the autoclave, and introducing ammonia into the autoclave to produce smooth N-face or M-plane Gallium Nitride films and bulk GaN.
従来技術、競合技術の概要(英語) BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is related to a method and materials for growing N-face Gallium Nitride (GaN) or M-plane Gallium Nitride using ammonothermal growth techniques.
2. Description of the Related Art
The usefulness of gallium nitride (GaN) and its ternary and quaternary alloys incorporating aluminum and indium (AlGaN, InGaN, AlINGaN) has been well established for fabrication of visible and ultraviolet opto-electronic devices and high-power electronic devices.
These devices are typically grown epitaxially on heterogeneous substrates, such as sapphire and silicon carbide, by Vapor Phase Epitaxy (VPE) techniques such as Metal-Organic Chemical Vapor Deposition (MOCVD) and Molecular Beam Epitaxy (MBE).
The growth of device layers is usually initiated by growing a buffer layer on the substrate in the MOCVD or MBE reactor.
The buffer layer provides a smooth surface of GaN or AlN suitable for successive growth of device layers.
However, the buffer layer is usually a Ga-polar (Ga-face) surface, because growth along the N-polar (N-face) direction results in a rough surface in the VPE growth phase.
Commercially available GaN-based devices are all grown on Ga-polar surface (Gallium-face of the C-plane, also known as the (0001) plane).
Recently, however, several studies have pointed out many benefits of N-polar (the Nitrogen-face of the C-plane, also known as the (000-1) plane) devices.
Also, it has been pointed out that devices grown on M-plane, also known as the {10-10} plane have further advantages over Ga-polar or N-polar devices.
One major benefit of N-polar (N-face) growth is for p-type doping.
In Ga-polar (Ga-face) growth of Mg-doped GaN, the film polarity locally starts to invert to the N-polar (N-face) direction.
This phenomenon is known as inversion domains when the concentration of Mg exceeds a certain limit.
The inversion domains deteriorate the surface smoothness; therefore, a Ga-polar (Ga-face) film is limited in its hole concentrations.
Since high Mg doping favors N-polar (N-face) growth, using a N-polar (N-face) substrate is expected to attain higher Mg concentrations, and thus higher hole concentrations.
Opto-electronic devices with high p-type conduction will improve their efficiency by decreasing series resistance of the devices.
A second major benefit is the inverted polarization charge.
Although GaN-based High Electron Mobility Transistors (HEMTs) are currently available, their usage is very limited due to many unsolved problems.
GaN-based HEMTs currently available have high gate leakage and are typically depletion mode devices.
Transistors grown on N-face GaN would realize low gate leakage devices, devices that operate in enhancement mode (normally off mode), are crucial for power switching devices, low dispersion devices, and improved carrier confinement.
One of the major benefits of M-plane optical devices is the higher emission efficiency due to absence of polarization field.
Another major benefit of M-plane optical devices is that the optically active layer can contain more In, allowing longer wavelength emission.
This enables to realize green, yellow, even red color LEDs.
Despite these benefits, current technology is limited to Ga-polar (Ga-face) devices because of the poor surface smoothness of N-polar (N-face) surface or M-plane surface.
Therefore new technology to attain a smooth surface of N-polar (N-face) or M-plane GaN is needed to realize the next generation of high-performance devices such as ultra-high bright LEDs, low threshold current Laser Diodes (LDs), high-power high-speed signal transistors and high-power switching transistors.

特許請求の範囲(英語) [claim1]
1. A method for directly growing a non-Ga-polar surface of gallium nitride (GaN), comprising: placing a seed crystal of GaN having an exposed non-Ga-polar surface of GaN into an autoclave;
placing a mineralizer into the autoclave;
placing a source into the autoclave;
adding ammonia to the autoclave;
heating the autoclave; and
ammonothermally growing the GaN in the heated autoclave, using the mineralizer, source and ammonia, wherein the exposed non-Ga-polar surface of the GaN is smoother than a Ga-polar surface of the GaN.
[claim2]
2. The method of claim 1, wherein the mineralizer is selected from a group comprising NaNH2, KNH2, LiNH2, NH4Cl, NH4Br, and NH4I.
[claim3]
3. The method of claim 1, wherein the source comprises polycrystalline GaN.
[claim4]
4. The method of claim 1, wherein the autoclave is heated in zones.
[claim5]
5. The method of claim 4, wherein a first zone is heated to a first temperature and a second zone is heated to a second temperature.
[claim6]
6. The method of claim 5, wherein the source is placed in the first zone and the seed crystal of GaN having the exposed non-Ga polar surface of GaN is placed in the second zone.
[claim7]
7. The method of claim 6, wherein the non-Ga polar surface is an N-polar C-plane (000-1) surface.
[claim8]
8. The method of claim 6, wherein the non-Ga polar surface is an M-plane {10-10} surface.
[claim9]
9. The method of claim 6, wherein the non-Ga polar surface is an A-plane {11-20} surface.
[claim10]
10. The method of claim 6, wherein the non-Ga polar surface is a {10-11} surface.
[claim11]
11. The method of claim 6, wherein the non-Ga polar surface is a {10-1-1} surface.
[claim12]
12. The method of claim 6, wherein the non-Ga polar surface is a {11-22} surface.
[claim13]
13. The method of claim 6, wherein the non-Ga polar surface is a {11-2-2} surface.
[claim14]
14. The method of claim 1, wherein the source comprises Ga metal.
[claim15]
15. A method of fabricating a gallium nitride (GaN) substrate, comprising: ammonothermally growing a GaN substrate resulting in an exposed N-polar (N-face) or M-plane surface that is smoother than a Ga-polar (Ga-face) surface of the GaN substrate.
[claim16]
16. The method of claim 15, wherein the N-polar (N-face) or M-plane surface is smooth enough for growth of device layers.
[claim17]
17. The method of claim 16, wherein the N-polar (N-face) or M-plane surface is smooth enough for direct growth of device layers.
[claim18]
18. The method of claim 17, wherein the N-polar (N-face) or M-plane surface is smooth enough for direct growth of device layers without subsequent processing.
[claim19]
19. A method of fabricating an opto-electronic device comprising: fabricating a GaN substrate from a GaN bulk crystal grown ammonothermally on a GaN seed, wherein a growth surface of the GaN bulk crystal is not a Ga-polar surface and the growth surface as grown is smoother than a Ga-polar surface; and
growing one or more group III nitride layers on the growth surface of the GaN substrate.
[claim20]
20. The method of claim 19, wherein the growing step comprises: growing a plurality of n-type group III nitride layers on the growth surface;
growing at least one group III nitride light-emitting active layer on the plurality of n-type group III nitride layers; and
growing at least one p-type group III nitride layer having an Mg doping on the active layers.
[claim21]
21. The method of claim 20, wherein an Mg concentration of the Mg-doped layer is more than 1021 cm-3.
[claim22]
22. The method of claim 19, wherein the growth surface is an M-plane {10-10} surface.
[claim23]
23. The method of claim 19, wherein the growth surface is an A-plane {11-20} surface.
[claim24]
24. The method of claim 19, wherein the growth surface is a {10-11} surface.
[claim25]
25. The method of claim 19, wherein the growth surface is a {10-1-1} surface.
[claim26]
26. The method of claim 19, wherein the growth surface is a {11-22} surface.
[claim27]
27. The method of claim 19, wherein the growth surface is a {11-2-2} surface.
[claim28]
28. The method of claim 19, wherein the growth surface is a {20-21} surface.
[claim29]
29. A method for fabricating a GaN layer, comprising: utilizing an N-polar surface or an M-plane surface of the GaN layer as a growth surface, wherein the N-polar surface or the M-plane surface is prepared and directly exposed using an ammonothermal growth technique and the N-polar surface or the M-plane surface is smoother than a Ga-polar surface of the GaN layer.
[claim30]
30. The method of claim 29, further comprising growing one or more group-III nitride layers to the N-polar or M-plane surface of the GaN layer.
[claim31]
31. A method for growing a group-III nitride layer, comprising: ammonothermally growing a group-III nitride layer on a substrate, wherein the group-III nitride layer comprises an N-face of a C-plane (000-1) or a M-plane {10-10} that is directly exposed as a result of the growth of the group-III nitride layer and the N-face of the C-plane (000-1) or the M-plane {10-10} is smoother than a Ga-face of the C-plane (0001).
[claim32]
32. The method of claim 31, wherein the N-face of the C-plane (000-1) or the M-plane {10-10} is substantially co-planar with a surface of the substrate.
[claim33]
33. The method of claim 31, wherein the N-face of the C-plane (000-1) or the M-plane {10-10} is tilted with respect to a surface of the substrate.
[claim34]
34. The method of claim 31, wherein the N-face of the C-plane (000-1) or the M-plane {10-10} is tilted at an angle less than 10 degrees with respect to the surface of the substrate.
[claim35]
35. The method of claim 31, wherein the N-face of the C-plane (000-1) or the M-plane {10-10} directly accepts growth of at least one additional group-III nitride layer.
[claim36]
36. A method for fabricating a GaN substrate, comprising: directly growing a GaN substrate with an exposed N-face or M-plane surface that is of device quality using an ammonothermal growth method, wherein the exposed N-face or M-plane surface is smoother than a Ga-polar surface of the GaN substrate.
[claim37]
37. The method of claim 36, further comprising growing a group-III nitride layer on the substrate, wherein the group III nitride layer comprises an N-face of a C-plane (000-1) or M-plane {10-10} that is directly exposed as a result of the growth of the group-III nitride layer.
[claim38]
38. The method of claim 36, wherein the N-face or M-plane is substantially co-planar with the plane of the substrate, rather than substantially perpendicular.
[claim39]
39. The method of claim 36, wherein the N-face or M-plane is misaligned with the plane of the substrate.
[claim40]
40. The method of claim 36, wherein the group-III nitride layer directly accepts growth of at least one additional group-III nitride layer.
  • 発明者/出願人(英語)
  • HASHIMOTO TADAO
  • SATO HITOSHI
  • NAKAMURA SHUJI
  • UNIVERSITY OF CALIFORNIA
  • JAPAN SCIENCE AND TECHNOLOGY AGENCY
国際特許分類(IPC)
米国特許分類/主・副
  • 438/46
  • 117/88
  • 117/101
  • 117/216
  • 257/E21.09
  • 257/E29.089
  • 257/E33.03
  • 438/47
参考情報 (研究プロジェクト等) ERATO NAKAMURA Inhomogeneous Crystal AREA
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