# US 8,772,842 B2 · Semiconductor diodes with low reverse bias currents

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- Number: US 8,772,842 B2
- Document ID: US8772842B2
- Status: Granted
- Kind: B2
- Application number: 13/040,524
- Filed: 2011-03-04
- Published: 2012-09-06
- Granted: 2014-07-08
- Earliest claimed: 2011-03-04
- Assignees: Transphorm Inc.
- Applicants: Yuvaraj Dora
- Inventors: Yuvaraj Dora
- Web page: https://patentgrep.com/patent/US8772842B2

## CPC

- H10D 8/60: Schottky-barrier diodes
- H10D 8/00: Diodes (variable-capacitance diodes H10D1/64; gated diodes H10D12/00)
- H10D 8/053: {of heterojunction diodes or of tunnel diodes}
- H10D 30/015: {of FETs having heterojunction interface channels or heterojunction gate electrodes, e.g. HEMT}
- H10D 30/6738: {Schottky barrier electrodes}
- H10D 30/675: {Group III-V materials, Group II-VI materials, Group IV-VI materials, selenium or tellurium}
- H10D 62/824: comprising only Group III-V materials heterojunctions, e.g. GaN/AlGaN heterojunctions
- H10D 62/85: being Group III-V materials, e.g. GaAs
- H10D 62/8503: {Nitride Group III-V materials, e.g. AlN or GaN}
- H10D 64/111: {Field plates}
- H10D 64/64: Electrodes comprising a Schottky barrier to a semiconductor
- H10D 30/47: having two-dimensional [2D] charge carrier gas channels, e.g. nanoribbon FETs or high electron mobility transistors [HEMT]
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

A diode is described with a III-N material structure, an electrically conductive channel in the III-N material structure, two terminals, wherein a first terminal is an anode adjacent to the III-N material structure and a second terminal is a cathode in ohmic contact with the electrically conductive channel, and a dielectric layer over at least a portion of the anode. The anode comprises a first metal layer adjacent to the III-N material structure, a second metal layer, and an intermediary electrically conductive structure between the first metal layer and the second metal layer. The intermediary electrically conductive structure reduces a shift in an on-voltage or reduces a shift in reverse bias current of the diode resulting from the inclusion of the dielectric layer. The diode can be a high voltage device and can have low reverse bias currents.

## Claims

### Claim 1

A diode, comprising:
a III-N material structure;
an electrically conductive channel in the III-N material structure;
two terminals, wherein a first terminal is an anode adjacent to the III-N material structure, and a second terminal is a cathode in ohmic contact with the electrically conductive channel; and
a dielectric layer over at least a portion of the anode; wherein
the diode is configured such that in operation, when voltage at the anode is less than voltage at the cathode, the diode is in an OFF state and a reverse bias current flows between the anode and the cathode, and when voltage at the anode is greater than voltage at the cathode, the diode is in an ON state and a substantial current flows from the cathode into the anode through the electrically conductive channel;
and
the anode comprises a first metal layer comprising nickel adjacent to the III-N material structure, a second metal layer comprising gold, and an intermediary electrically conductive structure between the first metal layer and the second metal layer, the intermediary electrically conductive structure comprising a layer of gold adjacent to the first metal layer and a layer of nickel between the layer of gold and the second metal layer.

### Claim 2 (depends on 1)

The diode of claim 1, wherein the III-N material structure comprises a first III-N material layer and a second III-N material layer, and wherein the electrically conductive channel is a 2DEG channel induced in a region of the first III-N material layer adjacent the second III-N material layer as a result of a compositional difference between the first III-N material layer and the second III-N material layer.

### Claim 3 (depends on 2)

The diode of claim 2, wherein the first III-N material layer includes GaN.

### Claim 4 (depends on 3)

The diode of claim 3, wherein the second III-N material layer includes AlGaN or AlInGaN.

### Claim 5 (depends on 2)

The diode of claim 2, further including a third III-N material layer between the first III-N material layer and the second III-N material layer.

### Claim 6 (depends on 5)

The diode of claim 5, wherein the third material layer comprises AIN.

### Claim 7 (depends on 2)

The diode of claim 2, wherein the first III-N material layer and the second III-N material layer are group III-face or [0 0 0 1] oriented or group-III terminated semipolar layers, and the second III-N material layer is between the first III-N material layer and the dielectric layer.

### Claim 8 (depends on 2)

The diode of claim 2, wherein the first III-N material layer and the second III-N material layer are N-face or [0 0 0 1 bar] oriented or nitrogen-terminated semipolar layers, and the first III-N material layer is between the second III-N material layer and the dielectric layer.

### Claim 9 (depends on 1)

The diode of claim 1, further comprising a field plate connected to the anode.

### Claim 10 (depends on 1)

The diode of claim 1, wherein the dielectric layer comprises SiNx.

### Claim 11 (depends on 1)

The diode of claim 1, wherein the dielectric layer is between about 0.2 microns and 20 microns thick.

### Claim 12 (depends on 1)

The diode of claim 1, wherein the dielectric layer comprises a first dielectric layer and a second dielectric layer on a side of the first dielectric layer opposite the III-N material structure.

### Claim 13 (depends on 12)

The diode of claim 12, wherein the second dielectric layer comprises SiOyNz.

### Claim 14 (depends on 1)

The diode of claim 1, further comprising a dielectric passivation layer between the III-N material structure and the dielectric layer, the dielectric passivation layer contacting a surface of the III-N material structure between the anode and the cathode.

### Claim 15 (depends on 14)

The diode of claim 14, wherein the dielectric passivation layer comprises SiN.

### Claim 16 (depends on 14)

The diode of claim 14, further including an additional insulating layer between the dielectric layer and the dielectric passivation layer.

### Claim 17 (depends on 16)

The diode of claim 16, wherein the additional insulating layer comprises AlN.

### Claim 18 (depends on 1)

The diode of claim 1, wherein the intermediary electrically conductive structure results in reduced reverse bias current in the diode compared to a similar diode lacking the intermediary electrically conductive structure.

### Claim 19 (depends on 1)

The diode of claim 1, wherein the intermediary electrically conductive structure consists of the layer of gold, the layer of nickel, and a layer of titanium, wherein the layer of titanium is between the layer of nickel and the second metal layer.

### Claim 20 (depends on 1)

The diode of claim 1, further comprising an electrode-defining layer between the material structure and the dielectric layer, wherein the electrode-defining layer comprises an aperture with at least a portion of the anode in the aperture.

### Claim 21 (depends on 20)

The diode of claim 20, wherein the electrode-defining layer comprises SiNx.

### Claim 22 (depends on 20)

The diode of claim 20, wherein the anode includes a portion extending over a surface of the electrode-defining layer.

### Claim 23 (depends on 22)

The diode of claim 22, wherein the aperture in the electrode-defining layer includes a step, and the extending portion of the anode is over the step.

### Claim 24 (depends on 22)

The diode of claim 22, wherein the portion of the anode extending over the surface of the electrode-defining layer functions as a field plate.

### Claim 25 (depends on 1)

The diode of claim 1, wherein the diode is a high-voltage device.

### Claim 26 (depends on 1)

The diode of claim 1, wherein the second metal layer is thicker than the first metal layer.

### Claim 27 (depends on 26)

The diode of claim 26, wherein the layer of gold in the intermediary conductive structure is between about 3500 and 7500 Angstroms thick.

### Claim 28

A diode, comprising:
a III-N material structure;
an electrically conductive channel in the material structure;
two terminals, wherein a first terminal is an anode adjacent to the III-N material structure, and a second terminal is a cathode in ohmic contact with the electrically conductive channel;
a dielectric layer over at least a portion of the anode; and
a recess in the III-N material structure; wherein
at least a portion of the anode is in the recess; and
the anode includes a first metal layer comprising nickel adjacent to the III-N material structure, a second metal layer comprising gold, and an intermediary electrically conductive structure between the first metal layer and the second metal layer, the intermediary electrically conductive structure comprising a layer of gold adjacent to the first metal layer and a layer of nickel between the layer of gold and the second metal layer.

### Claim 29 (depends on 28)

The diode of claim 28, wherein the III-N material structure comprises a first III-N material layer and a second III-N material layer, the electrically conductive channel is a 2DEG channel induced in a region of the first III-N material layer adjacent the second III-N material layer as a result of a compositional difference between the first III-N material layer and the second III-N material layer, and the recess extends through the 2DEG channel.

### Claim 30 (depends on 28)

The diode of claim 28, wherein the recess extends at least 30 nanometers into the III-N material structure.

### Claim 31 (depends on 28)

The diode of claim 28, further comprising an electrode-defining layer which is between the III-N material structure and the dielectric layer.

### Claim 32 (depends on 31)

The diode of claim 31, wherein the electrode-defining layer comprises SiN.

### Claim 33 (depends on 31)

The diode of claim 31, further comprising a dielectric passivation layer between the III-N material structure and the electrode-defining layer, the dielectric passivation layer contacting a surface of the III-N material structure between the anode and the cathode.

### Claim 34 (depends on 33)

The diode of claim 33, wherein the dielectric passivation layer comprises SiN.

### Claim 35 (depends on 33)

The diode of claim 33, further comprising an additional insulating layer between the dielectric passivation layer and the electrode-defining layer.

### Claim 36 (depends on 35)

The diode of claim 35, wherein the additional insulating layer comprises AIN.

### Claim 37 (depends on 35)

The diode of claim 35, wherein the additional insulating layer is less than about 20 nanometers thick.

### Claim 38 (depends on 31)

The diode of claim 31, wherein the anode includes an extending portion which is over a surface of the electrode-defining layer.

### Claim 39 (depends on 38)

The diode of claim 38, wherein the recess is in the electrode-defining layer and includes a step, and the extending portion of the anode is over the step.

### Claim 40 (depends on 38)

The diode of claim 38, wherein the extending portion of the anode functions as a field plate.

### Claim 41 (depends on 28)

The diode of claim 28, wherein the intermediary conductive structure further includes a layer of titanium.

### Claim 42

A diode, comprising:
a III-N material structure;
an electrically conductive channel in the III-N material structure;
two terminals, wherein a first terminal is an anode adjacent to the III-N material structure, and a second terminal is a cathode in ohmic contact with the electrically conductive channel; and
a dielectric layer over at least a portion of the anode; wherein
the anode comprises a first metal layer comprising nickel adjacent to the III-N material structure, a second metal layer comprising gold, and an intermediary electrically conductive structure between the first metal layer and the second metal layer, the intermediary electrically conductive structure comprising a layer of gold adjacent to the first metal layer and a layer of nickel between the layer of gold and the second metal layer.

### Claim 43 (depends on 42)

The diode of claim 42, further comprising an electrode-defining layer which is between the III-N material structure and the dielectric layer.

### Claim 44 (depends on 43)

The diode of claim 43, wherein the electrode-defining layer includes a recess, and at least a portion of the anode is in the recess.

### Claim 45 (depends on 44)

The diode of claim 44, wherein the recess includes at least two steps, and the anode includes an extending portion that is over the at least two steps.

### Claim 46 (depends on 45)

The diode of claim 45, wherein the recess extends into the III-N material structure.

### Claim 47 (depends on 46)

The diode of claim 46, wherein the III-N material structure comprises a first III-N material layer and a second III-N material layer, the electrically conductive channel is a 2DEG channel induced in a region of the first III-N material layer adjacent the second III-N material layer as a result of a compositional difference between the first III-N material layer and the second III-N material layer, and the recess extends through the 2DEG channel.