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Fabrication of nonpolar indium gallium nitride thin films, heterostructures and devices by metalorganic chemical vapor deposition 実績あり

外国特許コード F110003772
整理番号 E06718US3
掲載日 2011年7月4日
出願国 アメリカ合衆国
出願番号 37047909
公報番号 20090146162
公報番号 8502246
出願日 平成21年2月12日(2009.2.12)
公報発行日 平成21年6月11日(2009.6.11)
公報発行日 平成25年8月6日(2013.8.6)
優先権データ
  • 11/621,479 (2007.1.9) US
  • 11/123,805 (2005.5.6) US
  • 60/569,749P (2004.5.10) US
発明の名称 (英語) Fabrication of nonpolar indium gallium nitride thin films, heterostructures and devices by metalorganic chemical vapor deposition 実績あり
発明の概要(英語) A method for the fabrication of nonpolar indium gallium nitride (InGaN) films as well as nonpolar InGaN-containing device structures using metalorganic chemical vapor deposition (MOVCD).
The method is used to fabricate nonpolar InGaN/GaN violet and near-ultraviolet light emitting diodes and laser diodes.
従来技術、競合技術の概要(英語) BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is related to compound semiconductor growth and device fabrication.
More particularly the invention relates to the growth and fabrication of indium gallium nitride (InGaN) containing electronic and optoelectronic devices by metalorganic chemical vapor deposition (MOCVD).
2. Description of the Related Art
(Note: This application references a number of different publications as indicated throughout the specification by reference numbers enclosed in brackets, e.g., [Ref. x].
A list of these different publications ordered according to these reference numbers can be found below in the section entitled "References." Each of these publications is incorporated by reference herein.)
The usefulness of gallium nitride (GaN) and its ternary and quaternary compounds incorporating aluminum and indium (AlGaN, InGaN, AlINGaN) has been well established for fabrication of visible and ultraviolet optoelectronic devices and high-power electronic devices.
These devices are typically grown epitaxially by growth techniques including molecular beam epitaxy (MBE), metalorganic chemical vapor deposition (MOCVD), or hydride vapor phase epitaxy (HVPE).
GaN and its alloys are most stable in the hexagonal würtzite crystal structure, in which the structure is described by two (or three) equivalent basal plane axes that are rotated 120 deg. with respect to each other (the a-axes), all of which are perpendicular to a unique c-axis.
FIG. 1 is a schematic of a generic hexagonal würtzite crystal structure 100 and planes of interest 102, 104, 106, 108 with these axes 110, 112, 114, 116 identified therein, wherein the fill patterns are intended to illustrate the planes of interest 102, 104 and 106, but do not represent the materials of the structure 100.
Group III and nitrogen atoms occupy alternating c-planes along the crystal's c-axis.
The symmetry elements included in the würtzite structure dictate that III-nitrides possess a bulk spontaneous polarization along this c-axis.
Furthermore, as the würtzite crystal structure is non-centrosymmetric, würtzite nitrides can and do additionally exhibit piezoelectric polarization, also along the crystal's c-axis.
Current nitride technology for electronic and optoelectronic devices employs nitride films grown along the polar c-direction.
However, conventional c-plane quantum well structures in III-nitride based optoelectronic and electronic devices suffer from the undesirable quantum-confined Stark effect (QCSE), due to the existence of strong piezoelectric and spontaneous polarizations.
The strong built-in electric fields along the c-direction cause spatial separation of electron and holes that in turn give rise to restricted carrier recombination efficiency, reduced oscillator strength, and red-shifted emission.
(Al,Ga,In)N quantum-well structures employing nonpolar growth directions, e.g., the 11 20 a-direction or 1 100 m-direction, provide an effective means of eliminating polarization-induced electric field effects in würtzite nitride structures since the polar axis lies within the growth plane of the film, and thus parallel to heterointerfaces of quantum wells.
In the last few years, growth of nonpolar (Al,Ga,In)N has attracted great interest for its potential use in the fabrication of nonpolar electronic and optoelectronic devices.
Recently, nonpolar m-plane AlGaN/GaN quantum wells grown on lithium aluminate substrates via plasma-assisted MBE and nonpolar a-plane AlGaN/GaN multi-quantum wells (MQWs) grown by both MBE and MOCVD on r-plane sapphire substrates showed the absence of polarization fields along the growth direction.
Thus, nonpolar III-nitride light emitting diodes (LEDs) and laser diodes (LDs) have the potential to perform significantly better compared to their polar counterpart.
Unfortunately, nonpolar InGaN growth has proven challenging.
Indeed, the literature contains only two reports of the successful growth of nonpolar InGaN: Sun, et al. [Ref 1], grew m-plane InGaN/GaN quantum well structures containing up to 10% In by MBE, and Chitnis, et al. [Ref. 2], grew a-plane InGaN/GaN quantum well structures by MOCVD.
Sun, et al's, paper [Ref 1] focused primarily on structural and photoluminescence characteristics of their material, and does not suggest that their InGaN film quality is sufficient to fabricate working devices.
Chitnis, et al's paper [Ref. 1] described a nonpolar GaN/InGaN light emitting diode structure.
However, the limited data given in the paper suggested their nonpolar InGaN material quality was extremely poor.
Indeed, their device displayed large shifts in emission intensity with varying injection current, poor diode current-voltage characteristics, and extreme detrimental heating effects that necessitated pulsing the current injection in order to test the device.
These poor characteristics most likely can be explained by deficient material quality.
The lack of successful nonpolar InGaN growth can be attributed to several factors.
First, the large lattice mismatches between InGaN and available substrates severely complicate InGaN heteroepitaxy.
Second, InGaN must generally be grown at comparatively lower temperatures than GaN due to the propensity for In to desorb from the growth surface at higher temperatures.
Unfortunately, nonpolar nitrides are typically grown above 900 deg. C. and more often above 1050 deg. C., temperatures at which In readily desorbs from the surface.
Third, high-quality nonpolar nitrides are typically grown at decreased pressures (<100 Torr) in order to stabilize the a- and m-planes relative to inclined facets.
However, it has been previously widely reported that c-plane InGaN should be grown at atmospheric pressure in order to enhance In incorporation and decrease carbon incorporation.
The present invention overcomes these challenges and for the first time yields high quality InGaN films and InGaN-containing devices by MOCVD.

特許請求の範囲(英語) [claim1]
1. A p-n junction device structure, comprising at least: a nonpolar oriented III-nitride substrate, wherein nonpolar III-nitride layers grown epitaxially on the nonpolar III-nitride substrate have a threading dislocation density below 109 cm-2 and a stacking fault density below 1 * 104 cm-1;
the nonpolar III-nitride layers, comprising at least one or more nonpolar oriented Indium-containing III-nitride layers, are deposited on or above a top surface of the nonpolar oriented III-nitride substrate; and
wherein a material quality of the nonpolar III-nitride layers enables the p-n junction device structure to function in response to direct current density above 43 amps per centimeter square.
[claim2]
2. The device structure of claim 1, wherein the nonpolar oriented Indium-containing III-nitride layers are a growth along a nonpolar III-nitride crystallographic direction.
[claim3]
3. The device structure of claim 1, further comprising a light-emitting diode (LED) structure or laser diode (LD) structure including the p-n junction, wherein the non-polar oriented Indium-containing III-nitride layers are one or more light-emitting active layers for the LED or LD structure, and the p-n junction emits optical power or electroluminescence in response to direct current.
[claim4]
4. The device structure of claim 3, wherein the active layers emit light having a wavelength in a range 360 nm-600 nm.
[claim5]
5. The device structure of claim 1, wherein the material quality enables an external quantum efficiency (EQE) of at least 0.4%.
[claim6]
6. The device structure of claim 1, wherein the material quality is characterized by an amount of one or more of the following: carbon contamination, threading dislocation, stacking fault dislocation, and Indium incorporation.
[claim7]
7. The device structure of claim 1, wherein: the nonpolar oriented Indium-containing III-nitride layers are one or more nonpolar active layers, and
a material quality of the nonpolar Indium-containing III-nitride layers enables a measurement of an amount of nonpolarity of the nonpolar oriented Indium-containing III-nitride layers.
[claim8]
8. The device structure of claim 7, wherein: (1) the device structure is a light-emitting device structure for emitting electroluminescence as a function of the drive current;
(2) the nonpolar oriented Indium-containing III-nitride layers are the active layers emitting the electroluminescence; and
(3) the amount of nonpolarity is measured by a blue-shift of an emission peak of the electroluminescence, with increasing drive current over a drive current range, wherein the blue-shift is reduced as compared to a blue-shift of an emission peak emitted by a c-plane light-emitting device structure.
[claim9]
9. The device structure of claim 1, wherein the device structure is a laser diode or light emitting diode structure having an absence of blue-shift of an emission peak when the direct current density is increased from at least 11 amps per centimeter square.
[claim10]
10. The device structure of claim 7, wherein the amount of nonpolarity is measured by an effective hole mass, in the nonpolar oriented Indium-containing III-nitride layers, which is reduced as compared to an effective hole mass in a c-plane Indium-containing III-nitride layer.
[claim11]
11. The device structure of claim 1, further comprising: a cap layer on or above the Indium-containing III-nitride layers; and
one or more III-nitride device layers on or above the cap layer, wherein the cap layer prevents Indium desorbing from the Indium-containing III-nitride layers when the III-nitride device layers are formed.
[claim12]
12. The device structure of claim 1, wherein the device structure is a light emitting diode (LED) or Laser Diode (LD) structure: capable of emitting 1.5 milliwatts of output power, and
having a linewidth of less than 25 nanometers at the direct current density of at least 111 Amps per centimeter square.
[claim13]
13. The device structure of claim 1, wherein the nonpolar oriented III-nitride substrate is a gallium nitride (GaN) substrate.
[claim14]
14. The device structure of claim 13, wherein the GaN substrate is an a-plane GaN substrate and the top surface is an a-plane of the GaN substrate.
[claim15]
15. The device structure of claim 13, wherein the GaN substrate is an m-plane GaN substrate and the top surface is an m-plane of the GaN substrate.
[claim16]
16. A method of fabricating a p-n junction device structure, comprising at least: growing nonpolar III-nitride layers epitaxially on or above a top surface of a nonpolar oriented III-nitride substrate, wherein: the nonpolar III-nitride layers comprise at least one or more nonpolar oriented Indium-containing III-nitride layers,
a material quality of the nonpolar III-nitride layers enables the p-n junction device structure to function in response to direct current density above 43 amps per centimeter square, and
the epitaxially grown nonpolar layers having a threading dislocation density below 109 cm-2 and a stacking fault density below 1 * 104 cm-1.
[claim17]
17. The method of claim 16, wherein the device structure is a light emitting diode or laser diode structure: grown on the substrate that is Gallium Nitride, and
having an External Quantum Efficiency (EQE) reduction of at most 20% at a direct current density of 111 Amps per centimeter square, as compared to a maximum EQE.
[claim18]
18. The method of claim 16, wherein the substrate is Gallium Nitride, the threading dislocation density is below 5 * 106 cm-2, and the stacking fault density is below 3 * 103 cm-1.
[claim19]
19. The device structure of claim 1, wherein the device structure is a light emitting diode or laser diode structure having an External Quantum Efficiency (EQE) reduction of at most 20% at a direct current density of 111 Amps per centimeter square, as compared to a maximum EQE.
[claim20]
20. The device structure of claim 1, wherein the threading dislocation density is below 5 * 106cm-2 and the stacking fault density is below 3 * 103cm-1.
[claim21]
21. The method of claim 16, wherein the p-n junction is grown by metal organic vapor phase deposition (MOCVD).
[claim22]
22. The method of claim 16, wherein the nonpolar oriented III-nitride substrate is grown by hydride vapor phase epitaxy.
  • 発明者/出願人(英語)
  • CHAKRABORTY ARPAN
  • HASKELL BENJAMIN A
  • KELLER STACIA
  • SPECK JAMES S
  • DENBAARS STEVEN P
  • NAKAMURA SHUJI
  • MISHRA UMESH K
  • UNIVERSITY OF CALIFORNIA
  • JAPAN SCIENCE AND TECHNOLOGY AGENCY
国際特許分類(IPC)
米国特許分類/主・副
  • 257/97
  • 257/E33.003
  • 257/E33.025
  • 257/E33.027
  • 257/E33.028
  • 257/E33.043
  • 438/47
参考情報 (研究プロジェクト等) ERATO NAKAMURA Inhomogeneous Crystal AREA
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