# US 9,437,726 B2 · Field effect transistor

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- Number: US 9,437,726 B2
- Document ID: US9437726B2
- Status: Granted
- Kind: B2
- Application number: 14/787,443
- Filed: 2014-05-16
- Published: 2016-04-28
- Granted: 2016-09-06
- Earliest claimed: 2013-07-19
- Assignees: Sharp Kabushiki Kaisha
- Applicants: Sharp Kabushiki Kaisha
- Inventors: Tetsuzo Nagahisa; Shinichi Handa
- Web page: https://patentgrep.com/patent/US9437726B2

## CPC

- H10D 30/4755: {having wide bandgap charge-carrier supplying layers, e.g. modulation doped HEMTs such as n-AlGaAs/GaAs HEMTs}
- 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 62/221: {of FETs}
- H10D 62/824: comprising only Group III-V materials heterojunctions, e.g. GaN/AlGaN heterojunctions
- H10D 62/854: further characterised by the dopants
- H10D 62/364: {of IGFETs}
- H10D 62/8503: {Nitride Group III-V materials, e.g. AlN or GaN}
- H10D 64/256: {for lateral devices wherein the source or drain electrodes are recessed in semiconductor bodies (source or drain electrodes of TFTs H10D30/673)}
- H10D 64/693: {the insulator comprising nitrogen, e.g. nitrides, oxynitrides or nitrogen-doped materials}
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

In a field effect transistor, a carbon concentration in a buffer layer at the side closer to a high resistance layer is not less than 0.8×1019/cm3 and not more than 1.0×1021/cm3, a carbon concentration in the high resistance layer at the side closer to the buffer layer is not less than 3.7×1018/cm3 and not more than 1.0×1021/cm3, and a carbon concentration in the high resistance layer at the side closer to the channel layer is not less than 1.4×1019/cm3 and not more than 1.0×1021/cm3.

## Claims

### Claim 1

A field effect transistor comprising:
a substrate;
a buffer layer laminated on the substrate and having a multilayer structure formed by AlxGa1-xN and AlyGa1-yN (0≦x<1, 0≦y<1, and x≠y);
a high resistance layer laminated on the buffer layer and made of GaN containing carbon;
a channel layer laminated on the high resistance layer;
a nitride semiconductor layer laminated on the channel layer and serving as a barrier layer;
a source electrode and a drain electrode disposed on the nitride semiconductor layer in an arrangement spaced from each other; and
a gate electrode formed between the source electrode and the drain electrode and on the nitride semiconductor layer, the gate electrode being connected to the nitride semiconductor layer directly or with an insulating film interposed therebetween,
wherein a carbon concentration in the buffer layer at side closer to the high resistance layer is not less than 0.8×1019/cm3 and not more than 1.0×1021/cm3,
a carbon concentration in the high resistance layer at side closer to the buffer layer is not less than 3.7×1018/cm3 and not more than 1.0×1021/cm3, and
a carbon concentration in the high resistance layer at side closer to the channel layer is not less than 1.4×1019/cm3 and not more than 1.0×1021/cm3, and
the carbon concentration in the high resistance layer gradually increases toward the channel layer from side close to the buffer layer.

### Claim 2 (depends on 1)

The field effect transistor according to claim 1,
wherein the carbon concentration in the buffer layer at the side closer to the high resistance layer is not less than 1.2×1019/cm3,
the carbon concentration in the high resistance layer at the side closer to the buffer layer is not less than 4.4×1018/cm3, and
the carbon concentration in the high resistance layer at the side closer to the channel layer is not less than 1.6×1019/cm3.

### Claim 3 (depends on 1)

The field effect transistor according to claim 1,
wherein the carbon concentration in the buffer layer at the side closer to the high resistance layer is not less than 1.6×1019/cm3,
the carbon concentration in the high resistance layer at the side closer to the buffer layer is not less than 5.4×1018/cm3, and
the carbon concentration in the high resistance layer at the side closer to the channel layer is not less than 1.9×1019/cm3.

### Claim 4 (depends on 2)

The field effect transistor according to claim 2,
wherein the carbon concentration in the buffer layer at the side closer to the high resistance layer is not less than 1.6×1019/cm3,
the carbon concentration in the high resistance layer at the side closer to the buffer layer is not less than 5.4×1018/cm3, and
the carbon concentration in the high resistance layer at the side closer to the channel layer is not less than 1.9×1019/cm3.