# US 11,114,554 B2 · High-electron-mobility transistor having a buried field plate

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 11,114,554 B2
- Document ID: US11114554B2
- Status: Granted
- Kind: B2
- Application number: 15/635,695
- Filed: 2017-06-28
- Published: 2017-12-21
- Granted: 2021-09-07
- Earliest claimed: 2014-09-05
- Assignees: Infineon Technologies Austria AG
- Applicants: Infineon Technologies Austria AG
- Inventors: Gerhard Prechtl; Clemens Ostermaier; Oliver Häberlen
- Web page: https://patentgrep.com/patent/US11114554B2

## CPC

- H10D 30/4755: {having wide bandgap charge-carrier supplying layers, e.g. modulation doped HEMTs such as n-AlGaAs/GaAs HEMTs}
- 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 62/117: {Shapes of semiconductor bodies}
- H10D 62/357: {of FETs}
- 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}
- H10D 64/117: {Recessed field plates, e.g. trench field plates or buried field plates}
- H10P 14/3416: {Nitrides}
- H10P 50/246: {of Group III-V materials}
- H10P 50/646: {of Group III-V materials}
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10

## Abstract

A high-electron-mobility semiconductor device includes: a buffer region having first, second and third cross-sections forming a stepped lateral profile, the first cross-section being thicker than the third cross-section and comprising a first buried field plate disposed therein, the second cross-section interposed between the first and third cross-sections and forming oblique angles with the first and third cross-sections; and a barrier region of substantially uniform thickness extending along the stepped lateral profile of the buffer region, the barrier region being separated from the first buried field plate by a portion of the buffer region. The buffer region is formed by a first semiconductor material and the barrier region is formed by a second semiconductor material. The first and second semiconductor materials have different band-gaps such that an electrically conductive channel including a two-dimensional charge carrier gas arises at an interface between the buffer and barrier regions due to piezoelectric effects.

## Claims

### Claim 1

A high-electron-mobility semiconductor device, the device comprising:
a buffer region comprising first, second and third cross-sections forming a stepped lateral profile, the first cross-section being thicker than the third cross-section and comprising a first buried field plate disposed therein, the second cross-section interposed between the first and third cross-sections and forming oblique angles with the first and third cross-sections;
a barrier region of uniform thickness extending along the stepped lateral profile of the buffer region, the barrier region separated from the first buried field plate by a portion of the buffer region;
a source electrode on the first cross-section and in ohmic contact with the channel;
a gate electrode on the first cross-section, the gate electrode being spaced apart from the channel by the barrier region; and
a drain electrode disposed outside of the first and second cross-sections and in ohmic contact with the channel,
wherein the buffer region comprises a first semiconductor material and the barrier region comprises a second semiconductor material, the first and second semiconductor materials having different band-gaps such that an electrically conductive channel comprising a two-dimensional charge carrier gas arises at an interface between the buffer and barrier regions due to piezoelectric effects,
wherein, in the absence of external bias to the channel, the channel extends completely across the second cross-section from the first cross-section to the third cross section.

### Claim 2 (depends on 1)

The high-electron-mobility semiconductor device of claim 1, wherein a first angle at a lateral surface of the buffer layer at a transition between the first and second cross-sections is between twenty and seventy degrees, and wherein a second angle at the lateral surface of the buffer layer at a transition between the first and second cross-sections is between twenty and seventy degrees.

### Claim 3 (depends on 1)

The high-electron-mobility semiconductor device of claim 1, further comprising:
a capping layer comprising the first semiconductor material and covering the barrier region along the stepped lateral profile;
an electrically insulating passivation layer covering the capping layer along the stepped lateral profile; and
a first field plate electrode extending through the barrier and buffer regions and being in ohmic contact with the first buried field plate.

### Claim 4 (depends on 3)

The high-electron-mobility semiconductor device of claim 3, wherein the source electrode is arranged on the first cross-section, and wherein the drain electrode is arranged on a fifth cross-section of the buffer region being equal in thickness to the first cross-section such that the source and drain electrodes adjoin the barrier region along the same lateral plane.

### Claim 5 (depends on 3)

The high-electron-mobility semiconductor device of claim 3, further comprising a backbarrier region comprising the second semiconductor material, the backbarrier region arranged opposite to the barrier region and insulated from the two-dimensional charge carrier gas by the buffer region.

### Claim 6 (depends on 3)

The high-electron-mobility semiconductor device of claim 3, further comprising:
a second buried field plate in the fifth cross-section and spaced apart from the barrier region by portion of the buffer region; and
a second field plate electrode extending through the barrier and buffer regions and being in ohmic contact with the field plate.

### Claim 7 (depends on 6)

The high-electron-mobility semiconductor device of claim 6, wherein the source electrode and the first field plate electrode laterally overlap in the first cross-section, and wherein the drain electrode and the second field plate electrode laterally overlap and the fifth cross-section.

### Claim 8 (depends on 3)

The high-electron-mobility semiconductor device of claim 3, wherein the first buried field plate is formed from a doped region of first semiconductor material.

### Claim 9 (depends on 1)

The high-electron-mobility semiconductor device of claim 1, wherein the first semiconductor material is gallium nitride, wherein the second semiconductor material is aluminum gallium nitride, wherein the first buried field plate is formed from p-type gallium nitride, and wherein the barrier region is separated from the buried field plate by a portion gallium nitride in the buffer region.

### Claim 10 (depends on 1)

The high-electron-mobility semiconductor device of claim 1, wherein the buried field plate comprises an epitaxially grown second layer of the first or second semiconductor material on a first layer of the first semiconductor material as part of the buffer region.

### Claim 11

A high-electron-mobility semiconductor device, the device comprising:
a buffer region comprising first, second and third cross-sections forming a stepped lateral profile, the first cross-section being thicker than the third cross-section and comprising a first buried field plate disposed therein, the second cross-section interposed between the first and third cross-sections and forming oblique angles with the first and third cross-sections; and
a barrier region of uniform thickness extending along the stepped lateral profile of the buffer region, the barrier region separated from the first buried field plate by a portion of the buffer region, the buffer region comprising a first semiconductor material having a different band-gap as a second semiconductor material from the barrier region such that an electrically conductive channel comprising a two-dimensional charge carrier gas arises at an interface between the buffer and barrier regions due to piezoelectric effects;
a first electrode disposed on the first cross-section and in ohmic contact with the channel;
a second electrode disposed outside of the first and second cross-sections and in ohmic contact with the channel; and
a gate electrode disposed on the first cross-section that is laterally spaced apart from the second cross-section, the gate electrode being configured to control a conductive connection between the first and second electrodes by controlling a conductive state of the channel,
wherein, in the absence of external bias to the channel, the channel extends completely across the second cross-section from the first cross-section to the third cross section.