# US 12,002,881 B2 · Heterostructure for a high electron mobility transistor and a method of producing the same

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- Number: US 12,002,881 B2
- Document ID: US12002881B2
- Status: Granted
- Kind: B2
- Application number: 16/632,347
- Filed: 2017-07-20
- Published: 2020-06-25
- Granted: 2024-06-04
- Earliest claimed: 2017-07-20
- Assignees: Swegan AB
- Applicants: Swegan AB
- Inventors: Jr-Tai Chen; Olof Kordina
- Web page: https://patentgrep.com/patent/US12002881B2

## CPC

- H10D 30/4755: {having wide bandgap charge-carrier supplying layers, e.g. modulation doped HEMTs such as n-AlGaAs/GaAs HEMTs}
- H10P 14/2904: {Silicon carbide}
- H10D 30/015: {of FETs having heterojunction interface channels or heterojunction gate electrodes, e.g. HEMT}
- 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}
- H10D 62/815: of structures having periodic or quasi-periodic potential variation, e.g. superlattices or multiple quantum wells [MQW]
- H10D 62/8164: {comprising only semiconductor materials (potential variation in long-range structurally-disordered materials H10D62/8163)}
- H10D 62/824: comprising only Group III-V materials heterojunctions, e.g. GaN/AlGaN heterojunctions
- H10D 62/8503: {Nitride Group III-V materials, e.g. AlN or GaN}
- H10P 14/24: using chemical vapour deposition [CVD]
- H10P 14/3216: {Nitrides}
- H10P 14/3251: {consisting of three or more layers}
- H10P 14/3252: {Alternating layers, e.g. superlattice}
- H10P 14/3416: {Nitrides}
- H10P 14/3466: {Crystal orientation}
- H10P 14/3602: {In-situ cleaning}
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10

## Abstract

The present document discloses a heterostructure for a high electron mobility transistor (HEMT). The heterostructure comprises a SiC substrate, an InxAlyGa1-x-yN nucleation layer (12), wherein x=0-1, y=0-1, preferably x<0.05 and y>0.50, more preferably x<0.03 and y>0.70 and most preferably x<0.01 and y>0.90, formed on the SiC substrate. The heterostructure further comprises a GaN channel layer formed on the InxAlyGa1-x-yN nucleation layer. A thickness of the GaN channel layer is 50 to 500 nm, preferably 100 to 450 nm, most preferably 150 to 400 nm. The GaN channel layer presents a rocking curve with a (002) peak having a FMHW below 300 arcsec, and a rocking curve with a (102) peak having a FMHW below 400 arcsec as determined by X-ray diffraction, XRD. A surface of an uppermost layer of the heterostructure (1) exhibits an atomic step-flow morphology with rms roughness over a 10 μm2 scan area of below 1.8 nm, preferably below 1.4 nm, most preferably below 1 nm, over a 3 μm2 scan area of below 1 nm, preferably below 0.7 nm, most preferably below 0.4 nm, as determined by atomic force microscopy, AFM.

## Claims

### Claim 1

A heterostructure for a high electron mobility transistor (HEMT), comprising:
a SiC substrate,
an InxAlyGa1-x-yN nucleation layer, wherein x=0-1, y=0-1, formed directly on the SiC substrate, and
a GaN channel layer formed directly on the InxAlyGa1-x-yN nucleation layer, and
a barrier layer formed on the GaN channel layer,
wherein:
a thickness of the GaN channel layer is 50 to 500 nm;
a total thickness of the heterostructure, consisting of the InxAlyGa1-x-yN nucleation layer, the GaN channel layer, and the barrier layer, not including a thickness of the SiC substrate, is in a range of 54 nm to 730 nm;
the InxAlyGa1-x-yN nucleation layer is fully strained, wherein its in-plane lattice constant is exactly the same as an in-plane lattice constant of the SiC substrate, or is within +/−0.15% of an in-plane lattice constant of the SiC substrate;
the GaN channel layer presents a rocking curve with a (002) peak having a full width half maximum (FWHM) below 300 arcsec, and a rocking curve with a (102) peak having a FWHM below 400 arcsec as determined by X-ray diffraction (XRD); and
a surface of the GaN channel layer of the heterostructure prior to formation of any additional layers thereon exhibits root mean square (RMS) roughness of below 1.8 nm over a 10×10 μm2 scan area, or of below 1 nm over a 3×3 μm2 scan area.

### Claim 2 (depends on 1)

The heterostructure according to claim 1, wherein the InxAlyGa1-x-yN nucleation layer has a homogenous or varying content of Al.

### Claim 3 (depends on 1)

The heterostructure according to claim 1, further comprising an AlN exclusion layer formed on the GaN channel layer, and the barrier layer formed on the AlN exclusion layer.

### Claim 4 (depends on 3)

The heterostructure according to claim 3, further comprising a passivation layer of SiN or GaN formed on the barrier layer.

### Claim 5 (depends on 1)

The heterostructure according to claim 1, wherein an unintentional doping concentration of carbon in the GaN channel layer is less than 1E+17 cm−2.

### Claim 6 (depends on 1)

A method of producing a heterostructure according to claim 1, by metal organic chemical vapor deposition (MOCVD), for a high electron mobility transistor (HEMT), the method comprising:
providing a SiC substrate,
providing an InxAlyGa1-x-yN nucleation layer, wherein x=0-1, y=0-1, formed directly on the SiC substrate,
providing a GaN channel layer formed directly on the InxAlyGa1-x-yN nucleation layer, and
providing a barrier layer formed on the GaN channel layer,
wherein the pressure upon growth of the InxAlyGa1-x-yN nucleation layer and of the GaN channel layer is 20 to 200 mbar,
the temperature upon growth of the InxAlyGa1-x-yN nucleation layer is 900 to 1200° C., and
the temperature upon growth of the GaN channel layer is 1000 to 1150° C.

### Claim 7 (depends on 6)

The method of producing a heterostructure for a high electron mobility transistor (HEMT) according to claim 6, comprising a further step of providing an AlGaN exclusion layer, wherein the Al content is 40 to 80%, between the barrier layer and the GaN channel layer.

### Claim 8 (depends on 6)

The method of producing a heterostructure for a high electron mobility transistor (HEMT) according to claim 6, comprising a further step of providing a passivation layer of SiN or GaN on the barrier layer.

### Claim 9 (depends on 8)

A method of producing a HEMT device, comprising the steps of providing a heterostructure according to claim 8, and providing a source, a gate contact and a drain contact onto the passivation layer.

### Claim 10 (depends on 9)

The method according to claim 9, further comprising the step of providing an insulating layer between the passivation layer and the gate contact.

### Claim 11 (depends on 1)

A method of producing a heterostructure according to claim 1, by metal organic chemical vapor deposition (MOCVD), for a high electron mobility transistor (HEMT), the method comprising the steps of:
providing a SiC substrate;
growing an InxAlyGa1-x-yN nucleation layer, wherein x=0-1, y=0-1, directly on the SiC substrate;
growing a GaN channel layer directly on the InxAlyGa1-x-yN nucleation layer; and
growing a barrier layer on the GaN channel layer.

### Claim 12 (depends on 11)

The method of claim 11, wherein the InxAlyGa1-x-yN nucleation layer has a homogenous or varying content of Al.

### Claim 13 (depends on 11)

The method of claim 11, further comprising forming an AlN exclusion layer on the GaN channel layer, and forming the barrier layer on the AlN exclusion layer.

### Claim 14 (depends on 13)

The method of claim 13, further comprising forming a passivation layer of SiN or GaN on the barrier layer.