# US 4,398,963 A · Method for making non-alloyed heterojunction ohmic contacts

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- Number: US 4,398,963 A
- Document ID: US4398963A
- Status: Granted
- Kind: A
- Application number: 06/208,596
- Filed: 1980-11-19
- Granted: 1983-08-16
- Earliest claimed: 1980-11-19
- Assignees: The United States of America as represented by the Secretary of the Navy
- Inventors: Richard A. Stall; Colin E. C. Wood; Lester F. Eastman
- Web page: https://patentgrep.com/patent/US4398963A

## CPC

- H10D 62/85: being Group III-V materials, e.g. GaAs
- H10D 64/0116: {to Group III-V semiconductors}
- H10D 64/62: Electrodes ohmically coupled to a semiconductor
- H10D 62/854: further characterised by the dopants
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

Ultra low resistance heterojunction ohmic contacts to semiconductors such gallium arsenide (GaAs) is described wherein a single crystal layer of germanium degenerately doped with arsenic is deposited on gallium arsenide using molecular-beam epitaxy (MBE). A metallic film is then deposited over the single crystal layer of heavily doped germanium so as to obtain a non-alloyed heterojunction ohmic contact having a very low specific resistance.

## Claims

### Claim 1

A method of making a non-alloyed low resistance phmic contact having specific contact resistance less than 10.sup.-7 ohm-cm.sup.2 and including a substrate of a semiconductor, a degenerately doped single crystal layer of a material having matching lattice structure to that of said semiconductor and a metallic layer which includes the steps of:
growing the substrate of said semiconductor;
depositing a single crystal layer of degenerately doped material having a doping density exceeding 10.sup.20 cm.sup.-3 over the substrate of said semiconductor; and
evaporating the metallic layer over the single crystal layer of said degenerately doped material.

### Claim 2 (depends on 1)

The method of claim 1 wherein the step of depositing the single crystal layer of the degenerately doped material includes depositing a single crystal layer of Ge thickness 250 A over said substrate using molecular beam epitaxy (MBE).

### Claim 3 (depends on 2)

The method of claim 2 wherein the step of depositing the single crystal layer of the degenerately doped Ge includes creating doping density of at least 10.sup.20 cm.sup.-3 in said single crystal layer using an ion implantation technique.

### Claim 4 (depends on 1)

The method of claim 1 wherein the step of depositing the single crystal layer of the degenerately doped material includes the step of evaporating As for making single crystal layer of Ge as degenerately doped material in an evaporator.

### Claim 5 (depends on 2)

The method of claim 2 which further includes depositing a gold layer of thickness 2000 A over the degenerately doped layer of Ge of thickness 250 A.