TOP > 外国特許検索 > Defect reduction of non-polar and semi-polar III-Nitrides with sidewall lateral epitaxial overgrowth (SLEO)

Defect reduction of non-polar and semi-polar III-Nitrides with sidewall lateral epitaxial overgrowth (SLEO)

外国特許コード F110003763
整理番号 E06713US1
掲載日 2011年7月4日
出願国 アメリカ合衆国
出願番号 44408406
公報番号 20060270076
公報番号 7361576
出願日 平成18年5月31日(2006.5.31)
公報発行日 平成18年11月30日(2006.11.30)
公報発行日 平成20年4月22日(2008.4.22)
優先権データ
  • 60/685,952P (2005.5.31) US
発明の名称 (英語) Defect reduction of non-polar and semi-polar III-Nitrides with sidewall lateral epitaxial overgrowth (SLEO)
発明の概要(英語) A method of reducing threading dislocation densities in non-polar such as a-{11-20} plane and m-{1-100} plane or semi-polar such as {10-1n} plane III-Nitrides by employing lateral epitaxial overgrowth from sidewalls of etched template material through a patterned mask.
The method includes depositing a patterned mask on a template material such as a non-polar or semi polar GaN template, etching the template material down to various depths through openings in the mask, and growing non-polar or semi-polar III-Nitride by coalescing laterally from the tops of the sidewalls before the vertically growing material from the trench bottoms reaches the tops of the sidewalls.
The coalesced features grow through the openings of the mask, and grow laterally over the dielectric mask until a fully coalesced continuous film is achieved.
従来技術、競合技術の概要(英語) BACKGROUND OF THE INVENTION
1.
Field of the Invention
The present invention relates to defect reduction of non-polar and semi-polar III-Nitrides with sidewall lateral epitaxial overgrowth (SLEO).
2. Description of the Related Art
Gallium nitride (GaN) and its ternary and quaternary compounds are prime candidates for fabrication of visible and ultraviolet high-power and high-performance optoelectronic devices and electronic devices.
These devices are typically grown epitaxially as thin films by growth techniques including molecular beam epitaxy (MBE), metalorganic chemical vapor deposition (MOCVD), or hydride vapor phase epitaxy (HVPE).
The selection of substrates is critical for determining the III-Nitride growth direction.
Some of the most widely used substrates for nitride growth include SiC, Al2O3, and LiAlO2.
Various crystallographic orientations of these substrates are commercially available which cause a-plane, m-plane, or c-plane growth of GaN.
FIGS. 1(a) and 1(b) are schematics of crystallographic directions and planes of interest in hexagonal GaN.
Specifically, these schematics show the different crystallographic growth directions and also the planes of interest in the hexagonal wurtzite GaN structure, wherein FIG. 1(a) shows the crystallographic directions a1, a2, a3, c, <10-10> and <11-20>, and FIG. 1(b) shows planes a (11-20), m (10-10) and r (10-12).
The fill patterns of FIG. 1(b) are intended to illustrate the planes of interest, but do not represent the materials of the structure.
It is relatively easy to grow c-plane GaN due to its large growth window (pressure, temperature and precursor flows) and its stability.
Therefore, nearly all GaN-based devices are grown along the polar c-axis.
However, as a result of c-plane growth, each material layer suffers from separation of electrons and holes to opposite faces of the layers.
Furthermore, strain at the interfaces between adjacent layers gives rise to piezoelectric polarization, causing further charge separation.
FIGS. 2(a) and 2(b), which are schematics of band bending and electron hole separation as a result of polarization, show this effect, wherein FIG. 2(a) is a graph of energy (eV) vs. depth (nm) and represents a c-plane quantum well, while FIG. 2(b) is a graph of energy (eV) vs. depth (nm) and represents a non-polar quantum well.
Such polarization effects decrease the likelihood of electrons and holes recombining, causing the device to perform poorly.
One possible approach for eliminating piezoelectric polarization effects in GaN optoelectronic devices is to grow the devices on non-polar planes such as a-{11-20} and m-{1-100} plane.
Such planes contain equal numbers of Ga and N atoms and are charge-neutral.
Another reason why GaN materials perform poorly is the presence of defects due to lack of a lattice matched substrate.
Bulk crystals of GaN are not widely available so it is not possible to simply cut a crystal to present a surface for subsequent device regrowth.
All GaN films are initially grown heteroepitaxially, i.e., on foreign substrates that have a lattice mismatch to GaN.
There is an ever-increasing effort to reduce the dislocation density in GaN films in order to improve device performance.
The two predominant types of extended defects of concern are threading dislocations and stacking faults.
The primary means of achieving reduced dislocation and stacking fault densities in polar c-plane GaN films is the use of a variety of lateral overgrowth techniques, including single step and double step lateral epitaxial overgrowth (LEO, ELO, or ELOG), selective area epitaxy, cantilever and pendeo-epitaxy.
The essence of these processes is to block (by means of a mask) or discourage dislocations from propagating perpendicular to the film surface by favoring lateral growth over vertical growth.
These dislocation-reduction techniques have been extensively developed for c-plane GaN growth by HVPE and MOCVD.
The present invention is the first-ever successful execution of sidewall lateral epitaxial overgrowth (SLEO) of non-polar a-plane and m-plane GaN by any growth technique.
Prior to the invention described herein, SLEO of a-plane and/or m-plane GaN had not been demonstrated.

特許請求の範囲(英語) [claim1]
1. A method of reducing threading dislocation densities in non-polar and semi-polar III-Nitride material, comprising:
(a) performing a lateral epitaxial overgrowth of non-polar or semi-polar III-Nitride material from sidewalls of etched template material through a patterned mask.
[claim2]
2. The method of claim 1, wherein the material is any non-polar or semi-polar crystal orientation of III-Nitride material.
[claim3]
3. The method of claim 1, further comprising:
(1) forming the patterned mask on the template material;(2) etching the template material through one or more openings in the patterned mask to form one or more trenches or pillars in the template material, wherein the trenches or pillars define the sidewalls;
and(3) growing the non-polar or semi-polar III-Nitride material laterally from tops of the sidewalls and vertically from bottoms of the trenches, wherein the III-Nitride material growing laterally from the tops of the sidewalls coalesces before the III-Nitride material growing vertically from the bottoms of the trenches reaches the tops of the sidewalls.
[claim4]
4. The method of claim 3, wherein the non-polar or semi-polar III-Nitride material growing laterally from the tops of the sidewalls blocks the non-polar or semi-polar III-Nitride material growing vertically from the bottoms of the trenches.
[claim5]
5. The method of claim 3, wherein the openings are aligned to create planar sidewalls in subsequent lateral growth steps.
[claim6]
6. The method of claim 3, wherein the template material has a thickness comparable or scaled relative to the openings' dimensions to compensate for competing lateral to vertical growth rates.
[claim7]
7. The method of claim 6, wherein the etching is performed to one or more etch depths comparable or scaled to the openings' dimensions in order for the non-polar or semi-polar III-Nitride material growing from the tops of the sidewalls to coalesce before the non-polar or semi-polar III-Nitride material growing from the bottoms of the trenches reaches the tops of the sidewalls.
[claim8]
8. The method of claim 3, wherein the non-polar or semi-polar III-Nitride material grows vertically up through the openings after coalescence.
[claim9]
9. The method of claim 3, wherein the non-polar or semi-polar III-Nitride material grows through the openings after coalescence, and then grows laterally over the patterned mask to form an overgrown non-polar or semi-polar III-Nitride film.
[claim10]
10. The method of claim 9, wherein dislocation densities are reduced by eliminating or reducing defects in the overgrown non-polar or semi-polar III-Nitride material.
[claim11]
11. The method of claim 3, further comprising reducing dislocation densities at least one order of magnitude lower than that achieved in III-Nitride materials using conventional single step lateral epitaxial overgrowth.
[claim12]
12. The method of claim 3, wherein: to control a lateral and vertical growth rate, growth conditions for a-{11-20} plane gallium nitride (GaN) films are specified by: a temperature in a range of 1000-1250 deg. C., a reactor pressure in a range of 20-760 Torr, and a V/III ratio in a range of 100-3500 at different stages of the growth, wherein the growth conditions are such that the lateral growth rate is greater than the vertical growth rate.
[claim13]
13. The method of claim 3, wherein the non-polar or semi-polar III-Nitride material grows only from regions of exposed template material, but not on the patterned mask.
[claim14]
14. The method of claim 3;
further comprising: decreasing stacking fault densities with an anisotropy factor, by encouraging higher growth rates on a gallium (Ga) face of the non-polar III-Nitride material and limiting growth rates on a nitrogen (N) face of the non-polar III-Nitride material, thereby reducing stacking fault densities at least one order of magnitude lower than that achieved in Nitride material using conventional single step lateral epitaxial overgrowth, and confining stacking faults to N faces.
[claim15]
15. The method of claim 3, further comprising: preventing growth from the bottoms of the trenches by etching to a substrate or depositing an additional mask on the bottoms of the trenches.
[claim16]
16. A device, wafer, substrate or template manufactured using the method of claim 1.
[claim17]
17. A method of reducing threading dislocation densities in epitaxially grown non-polar or semi-polar III-Nitride films, devices or substrates, comprising:
(a) performing a lateral epitaxial overgrowth of epitaxial material from sidewalls of etched template material through a patterned mask, comprising:
(1) forming the patterned mask on the template material;(2) etching the template material through one or more openings in the patterned mask to form one or more trenches or pillars in the template material, the one or more trenches or pillars comprising the sidewalls, tops of the sidewalls and one or more bottoms;
and(3) growing and coalescing the epitaxial material laterally from the tops before epitaxial material vertically growing from the one or more bottoms reaches the tops;(4) growing the epitaxial material vertically up through the one or more openings after the growing and coalescing step (3);(5) growing the epitaxial material laterally over the patterned mask to form overgrown material which may form a continuous film, after the growing and coalescing step (3),wherein the growth in steps (3) and (5) is performed using a lateral overgrowth technique.
[claim18]
18. The method of claim 1, wherein the non-polar or semi-polar Ill-Nitride material is non-polar a-{11-20}plane, non-polar m-{1-100}plane, or semi-polar {10-1n}plane III-Nitride material.
  • 発明者/出願人(英語)
  • IMER BILGE M
  • SPECK JAMES S
  • DENBAARS STEVEN P
  • JAPAN SCIENCE AND TECHNOLOGY AGENCY
国際特許分類(IPC)
米国特許分類/主・副
  • 438/479
  • 257/E21.097
  • 257/E21.131
  • 257/E21.132
  • 257/E21.566
  • 438/41
  • 438/481
参考情報 (研究プロジェクト等) ERATO NAKAMURA Inhomogeneous Crystal AREA
ライセンスをご希望の方、特許の内容に興味を持たれた方は、問合せボタンを押してください。

PAGE TOP

close
close
close
close
close
close