# US 9,437,686 B2 · Gallium nitride devices with discontinuously graded transition layer

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- Number: US 9,437,686 B2
- Document ID: US9437686B2
- Status: Granted
- Kind: B2
- Application number: 14/579,738
- Filed: 2014-12-22
- Published: 2015-04-23
- Granted: 2016-09-06
- Earliest claimed: 2000-12-14
- Assignees: Infineon Technologies Americas Corp.
- Applicants: Infineon Technologies Americas Corp.
- Inventors: T. Warren Weeks, Jr.; Edwin Lanier Piner; Thomas Gehrke; Kevin J. Linthicum
- Web page: https://patentgrep.com/patent/US9437686B2

## CPC

- H10D 62/8164: {comprising only semiconductor materials (potential variation in long-range structurally-disordered materials H10D62/8163)}
- C30B 23/02: Epitaxial-layer growth
- C30B 23/025: {characterised by the substrate}
- C30B 25/02: Epitaxial-layer growth
- C30B 25/18: characterised by the substrate
- C30B 25/183: {being provided with a buffer layer, e.g. a lattice matching layer}
- C30B 29/06: Silicon
- C30B 29/403: {AIII-nitrides}
- C30B 29/406: {Gallium nitride}
- C30B 29/68: Crystals with laminate structure, e.g. "superlattices"
- H10D 30/015: {of FETs having heterojunction interface channels or heterojunction gate electrodes, e.g. HEMT}
- H10D 30/4755: {having wide bandgap charge-carrier supplying layers, e.g. modulation doped HEMTs such as n-AlGaAs/GaAs HEMTs}
- H10D 30/60: Insulated-gate field-effect transistors [IGFET] (H10D30/40 takes precedence)
- H10D 62/115: {Dielectric isolations, e.g. air gaps}
- H10D 62/40: Crystalline structures
- H10D 62/405: {Orientations of crystalline planes}
- H10D 62/824: comprising only Group III-V materials heterojunctions, e.g. GaN/AlGaN heterojunctions
- H10D 62/826: comprising only Group II-VI materials heterojunctions, e.g. CdTe/HgTe heterojunctions
- H10D 62/8503: {Nitride Group III-V materials, e.g. AlN or GaN}
- H10D 62/852: being Group III-V materials comprising three or more elements, e.g. AlGaN or InAsSbP
- H10H 20/0133: {with a substrate not being Group III-V materials}
- H10H 20/01335: {the light-emitting regions comprising nitride materials}
- H10H 20/0137: {the light-emitting regions comprising nitride materials}
- H10H 20/811: having quantum effect structures or superlattices, e.g. tunnel junctions
- H10H 20/812: within the light-emitting regions, e.g. having quantum confinement structures
- H10H 20/815: having stress relaxation structures, e.g. buffer layers
- H10H 20/825: containing nitrogen, e.g. GaN
- H10P 14/24: using chemical vapour deposition [CVD]
- H10P 14/2905: {Silicon, silicon germanium or germanium}
- H10P 14/2922: {being non-crystalline insulating materials, e.g. glass or polymers}
- H10P 14/2925: {Surface structures}
- H10P 14/2926: {Crystal orientations}
- H10P 14/3211: {Silicon, silicon germanium or germanium}
- H10P 14/3216: {Nitrides}
- H10P 14/3252: {Alternating layers, e.g. superlattice}
- H10P 14/3254: {Graded layers}
- H10P 14/3416: {Nitrides}
- H10P 14/3458: {Monocrystalline}
- H10D 30/475: {having wider bandgap layer formed on top of lower bandgap active layer, e.g. undoped barrier HEMTs such as i-AlGaN/GaN HEMTs}
- Y10T 428/24942: including components having same physical characteristic in differing degree
- Y10T 428/26: Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension
- Y10T 428/265: 1 mil or less
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
- C30B: SINGLE-CRYSTAL GROWTH (by using ultra-high pressure, e.g. for the formation of diamonds, B01J3/06); UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL (zone-refining of metals or alloys C22B); PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (casting of metals, casting of other substances by the same processes or devices B22D; working of plastics B29; modifying the physical structure of metals or alloys C21D, C22F); SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (for producing semiconductor devices or parts thereof H10); APPARATUS THEREFOR
- H10H: INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

The invention provides semiconductor materials including a gallium nitride material layer formed on a silicon substrate and methods to form the semiconductor materials. The semiconductor materials include a transition layer formed between the silicon substrate and the gallium nitride material layer. The transition layer is compositionally-graded to lower stresses in the gallium nitride material layer which can result from differences in thermal expansion rates between the gallium nitride material and the substrate. The lowering of stresses in the gallium nitride material layer reduces the tendency of cracks to form. Thus, the invention enables the production of semiconductor materials including gallium nitride material layers having few or no cracks. The semiconductor materials may be used in a number of microelectronic and optical applications.

## Claims

### Claim 1

A semiconductor structure formed by a method comprising:
forming a discontinuously graded transition layer comprising an alloy of gallium nitride consisting of AlxInyGa(1−x−y)N;
forming a gallium nitride layer over said transition layer.

### Claim 2 (depends on 1)

The semiconductor structure of claim 1, wherein a value of y of said transition layer is selected from the group consisting of zero and substantially zero.

### Claim 3 (depends on 1)

The semiconductor structure of claim 1, wherein a value of 1−x−y at a front surface of said transition layer is greater than a value of 1−x−y at a back surface of said transition layer.

### Claim 4

A semiconductor structure comprising:
a substrate;
an intermediate layer comprising a first aluminum nitride alloy formed above said substrate, said first aluminum nitride alloy being substantially free of gallium;
a transition layer including at least one compositionally-graded layer;
a gallium nitride layer formed over said transition layer.

### Claim 5 (depends on 4)

The semiconductor structure of claim 4 wherein said intermediate layer comprises a second aluminum nitride alloy situated between said first aluminum nitride alloy and said substrate.

### Claim 6 (depends on 4)

The semiconductor structure of claim 4 wherein said at least one compositionally-graded layer is graded discontinuously.

### Claim 7 (depends on 4)

The semiconductor structure of claim 4 wherein said transition layer comprises an alloy of gallium nitride selected from the group consisting of AlXInYGa(1−x−y)N, InYGa(1−y)N, and AlXGa(1−x)N.

### Claim 8 (depends on 4)

The semiconductor structure of claim 4 wherein said substrate comprises a silicon-on-insulator (SOI) substrate.

### Claim 9 (depends on 4)

The semiconductor structure of claim 4 wherein said substrate comprises a silicon-on-sapphire (SOS) substrate.

### Claim 10 (depends on 4)

The semiconductor structure of claim 4 wherein said substrate comprises a SIMOX substrate.

### Claim 11

A semiconductor structure comprising:
a substrate;
an intermediate layer comprising a first aluminum nitride alloy formed over at least one layer, said first aluminum nitride alloy being substantially free of gallium, said at least one layer being situated over said substrate;
a transition layer;
a gallium nitride layer formed over said transition layer.

### Claim 12 (depends on 11)

The semiconductor structure of claim 11 wherein said at least one layer comprises a second aluminum nitride alloy.

### Claim 13 (depends on 11)

The semiconductor structure of claim 11 wherein said transition layer comprises an alloy of gallium nitride selected from the group consisting of AlXInYGa(1−x−y)N, InYGa(1−y)N, and AlXGa(1−x)N.

### Claim 14 (depends on 11)

The semiconductor structure of claim 11 wherein a concentration of gallium in said transition layer is graded.

### Claim 15 (depends on 11)

The semiconductor structure of claim 11 wherein said substrate comprises a silicon-on-insulator (SOI) substrate.

### Claim 16 (depends on 11)

The semiconductor structure of claim 11 wherein said substrate comprises a silicon-on-sapphire (SOS) substrate.

### Claim 17 (depends on 11)

The semiconductor structure of claim 11 wherein said substrate comprises a SIMOX substrate.