# US 2014/0151748 A1 · Compound semiconductor device and manufacturing method of the same

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- Number: US 2014/0151748 A1
- Document ID: US20140151748A1
- Status: Published application
- Kind: A1
- Application number: 14/066,025
- Filed: 2013-10-29
- Published: 2014-06-05
- Earliest claimed: 2012-12-04
- Assignees: Fujitsu Limited
- Applicants: Fujitsu Limited
- Inventors: Masato Nishimori; Tadahiro Imada; Toshihiro Ohki
- Web page: https://patentgrep.com/patent/US20140151748A1

## CPC

- 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 62/343: {Gate regions of field-effect devices having PN junction gates}
- H10D 64/411: {for FETs}
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

The compound semiconductor device includes a first-compound-semiconductor-layer, a second-compound-semiconductor-layer formed on an upper side of the first-compound-semiconductor-layer and having a band gap larger than the band gap of the first-compound-semiconductor-layer, a p-type third-compound-semiconductor-layer formed on an upper side of the second-compound-semiconductor-layer, an electrode formed on an upper side of the second-compound-semiconductor-layer through the third-compound-semiconductor-layer, a fourth-compound-semiconductor-layer formed so as to be in contact with the third-compound-semiconductor-layer at an upper side of the second-compound-semiconductor-layer and having a band gap smaller than the band gap of the second-compound-semiconductor-layer, and a fifth-compound-semiconductor-layer formed so as to be in contact with the third-compound-semiconductor-layer at an upper side of the fourth-compound-semiconductor-layer and having a band gap larger than the band gap of the fourth-compound-semiconductor-layer.

## Claims

### Claim 1

A compound semiconductor device comprising:
a first compound semiconductor layer;
a second compound semiconductor layer formed on an upper side of the first compound semiconductor layer and having a band gap larger than the band gap of the first compound semiconductor layer;
a p-type third compound semiconductor layer formed on an upper side of the second compound semiconductor layer;
an electrode formed on an upper side of the second compound semiconductor layer through the third compound semiconductor layer;
a fourth compound semiconductor layer formed so as to be in contact with the third compound semiconductor layer at an upper side of the second compound semiconductor layer and having a band gap smaller than the band gap of the second compound semiconductor layer; and
a fifth compound semiconductor layer formed so as to be in contact with the third compound semiconductor layer at an upper side of the fourth compound semiconductor layer and having a band gap larger than the band gap of the fourth compound semiconductor layer.

### Claim 2 (depends on 1)

The compound semiconductor device of claim 1, wherein the fourth compound semiconductor layer and the fifth compound semiconductor layer are formed at a side surface of the third compound semiconductor layer.

### Claim 3 (depends on 2)

The compound semiconductor device of claim 2, further comprising:
a sixth compound semiconductor layer formed between the second compound semiconductor layer and the third compound semiconductor layer and having a band gap larger than the band gap of the fourth compound semiconductor layer.

### Claim 4 (depends on 1)

The compound semiconductor device of claim 1, wherein the fourth compound semiconductor layer is formed between the second compound semiconductor layer and the third compound semiconductor layer, and the fifth compound semiconductor layer is formed at a side surface of the third compound semiconductor layer.

### Claim 5 (depends on 4)

The compound semiconductor device of claim 4, wherein a part or an entire of the fourth compound semiconductor layer becomes p-type in a region where the fourth compound semiconductor layer is disposed below the third compound semiconductor layer.

### Claim 6 (depends on 1)

The compound semiconductor device of claim 1, wherein the fourth compound semiconductor layer and the fifth compound semiconductor layer are formed only at one side surface of the third compound semiconductor layer.

### Claim 7 (depends on 6)

The compound semiconductor device of claim 6, further comprising:
a connection electrode electrically connected to the fifth compound semiconductor layer.

### Claim 8

A method for manufacturing a compound semiconductor device, the method comprising:
providing a first compound semiconductor layer having a band gap;
forming a second compound semiconductor layer having a band gap larger than the band gap of the first compound semiconductor layer on an upper side of the first compound semiconductor layer;
forming a p-type third compound semiconductor layer on an upper side of the second compound semiconductor layer;
forming an electrode on an upper side of the second compound semiconductor layer through the third compound semiconductor layer;
forming a fourth compound semiconductor layer having a band gap smaller than the band gap of the second compound semiconductor layer so as to be in contact with the third compound semiconductor layer at an upper side of the second compound semiconductor layer; and
forming a fifth compound semiconductor layer having a band gap larger than the band gap of the fourth compound semiconductor layer so as to be in contact with the third compound semiconductor layer at an upper side of the fourth compound semiconductor layer.

### Claim 9 (depends on 8)

The method of claim 8, wherein the fourth compound semiconductor layer and the fifth compound semiconductor layer are formed at a side surface of the third compound semiconductor layer.

### Claim 10 (depends on 9)

The method of claim 9, further comprising:
forming a sixth compound semiconductor layer having a band gap larger than the band gap of the fourth compound semiconductor layer between the second compound semiconductor layer and the third compound semiconductor layer.

### Claim 11 (depends on 8)

The method of claim 8, wherein the fourth compound semiconductor layer is formed between the second compound semiconductor layer and the third compound semiconductor layer, and the fifth compound semiconductor layer is formed at a side surface of the third compound semiconductor layer.

### Claim 12 (depends on 11)

The method of claim 11, wherein a part or whole of the fourth compound semiconductor layer becomes p-type in a region where the fourth compound semiconductor layer is disposed below the third compound semiconductor layer.

### Claim 13 (depends on 8)

The method of claim 8, wherein the fourth compound semiconductor layer and the fifth compound semiconductor layer are formed only at one side surface of the third compound semiconductor layer.

### Claim 14 (depends on 13)

The method of claim 13, further comprising:
forming a connection electrode on the fifth compound semiconductor layer.

### Claim 15

A power supply circuit comprising: a transformer, and a low-voltage circuit and a high-voltage circuit across the transformer,
wherein the high-voltage circuit has a transistor, and
the transistor comprises:
a first compound semiconductor layer;
a second compound semiconductor layer formed on an upper side of the first compound semiconductor layer and having a band gap larger than the band gap of the first compound semiconductor layer;
a conductive p-type third compound semiconductor layer formed on an upper side of the second compound semiconductor layer;
an electrode formed on an upper side of the second compound semiconductor layer through the third compound semiconductor layer;
a fourth compound semiconductor layer formed so as to be in contact with the third compound semiconductor layer at an upper side of the second compound semiconductor layer and having a band gap smaller than the band gap of the second compound semiconductor layer; and
a fifth compound semiconductor layer formed so as to be in contact with the third compound semiconductor layer at an upper side of the fourth compound semiconductor layer and having a band gap larger than the band gap of the fourth compound semiconductor layer.

### Claim 16

A high frequency amplifier which amplifies and outputs a high frequency voltage input, the high frequency amplifier comprising:
a transistor,
wherein the transistor comprises:
a first compound semiconductor layer;
a second compound semiconductor layer formed on an upper side of the first compound semiconductor layer and having a band gap larger than the band gap of the first compound semiconductor layer;
a conductive p-type third compound semiconductor layer formed on an upper side of the second compound semiconductor layer;
an electrode formed on an upper side of the second compound semiconductor layer through the third compound semiconductor layer;
a fourth compound semiconductor layer formed so as to be in contact with the third compound semiconductor layer at an upper side of the second compound semiconductor layer and having a band gap smaller than the band gap of the second compound semiconductor layer; and
a fifth compound semiconductor layer formed so as to be in contact with the third compound semiconductor layer at an upper side of the fourth compound semiconductor layer and having a band gap larger than the band gap of the fourth compound semiconductor layer.