# US 11,444,216 B2 · Power photodiode structures, methods of making, and methods of use

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- Number: US 11,444,216 B2
- Document ID: US11444216B2
- Status: Granted
- Kind: B2
- Application number: 16/930,250
- Filed: 2020-07-15
- Published: 2021-01-21
- Granted: 2022-09-13
- Earliest claimed: 2019-07-15
- Assignees: SLT Technologies, Inc.
- Applicants: SLT Technologies, Inc
- Inventors: Drew W. Cardwell; Mark P. D'Evelyn
- Web page: https://patentgrep.com/patent/US11444216B2

## CPC

- H10F 77/16: Material structures, e.g. crystalline structures, film structures or crystal plane orientations
- H10F 10/144: comprising only Group III-V materials, e.g. GaAs,AlGaAs, or InP photovoltaic cells
- H10F 30/223: the potential barrier being a PIN barrier
- H10F 71/1274: {comprising nitrides, e.g. InGaN or InGaAlN}
- H10F 71/1278: {comprising nitrides, e.g. GaN}
- H10F 71/139: {using temporary substrates}
- H10F 77/1246: {III-V nitrides, e.g. GaN}
- H10F 77/12485: {comprising nitride compounds, e.g. InGaN}
- H10F 77/206: {for devices having potential barriers}
- H10F 77/413: {directly associated or integrated with the devices, e.g. back reflectors (directly associated or integrated with photovoltaic cells H10F77/42)}
- H10F 77/488: {Reflecting light-concentrating means, e.g. parabolic mirrors or concentrators using total internal reflection}
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION

## Abstract

According to the present disclosure, techniques related to manufacturing and applications of power photodiode structures and devices based on group-III metal nitride and gallium-based substrates are provided. More specifically, embodiments of the disclosure include techniques for fabricating photodiode devices comprising one or more of GaN, AlN, InN, InGaN, AlGaN, and AlInGaN, structures and devices. Such structures or devices can be used for a variety of applications including optoelectronic devices, photodiodes, power-over-fiber receivers, and others.

## Claims

### Claim 1

A photodiode structure, comprising:
a substrate having a first surface and a second surface, wherein
the second surface is opposite to the first surface,
the substrate is a single-crystalline group-III metal nitride, and
the first surface of the substrate has a crystallographic orientation within 5 degrees of (0001) +c-plane, {10-10} m-plane, or a semipolar plane selected from one of {11-2±2}, {60-6±1}, {50-5±1}, {40-4±1}, {30-3±1}, {50-5±2}, {70-7±3}, {20-2±1}, {30-3±2}, {40-4±3}, {50-5±4}, {10-1±1}, {1 0 −1 ±2}, {1 0 −1 ±3}, or differs from (000-1) by between 2 degrees and 5 degrees;
an n-type layer and a p-type layer that are disposed over the first surface of the substrate, wherein the n-type layer and the p-type layer each comprise AlxInyGa1-x-yN, where 0≤x, y, x+y≤1, and have a dopant concentration of at least 1×1016 cm−3;
one or more absorber layers disposed between the n-type and the p-type layers, wherein the one or more absorber layers comprise AlxInyGa1-x-yN, where 0≤x, y, x+y≤1 and have a dislocation density below about 109 cm−2;
a p-side electrical contact layer disposed over the p-type layer, wherein the p-side electrical contact layer has an average reflectance of at least 70% for at least one wavelength between 390 nanometers and 460 nanometers and a contact resistance below 3×10−3 Ωcm2;
an n-side electrical contact layer disposed over the second surface of the substrate, wherein the n-side electrical contact layer has an average reflectance of at least 70% for at least one wavelength between 390 nanometers and 460 nanometers and a contact resistance below 1×10−3 Ωcm2; and
a light receiving surface, wherein the light receiving surface is aligned to cause light, having at least one wavelength between 390 nanometers and 460 nanometers and incident on the light receiving surface at an angle, to be reflected at least once from the n-side electrical contact layer and from the p-side electrical contact layer, wherein the photodiode structure is characterized by a fill factor of at least 50%.

### Claim 2 (depends on 1)

The photodiode structure of claim 1, wherein the fill factor is achieved under an illumination level producing a current density of at least 10 A cm−2.

### Claim 3 (depends on 1)

The photodiode structure of claim 1, wherein the fill factor is at least 80%.

### Claim 4 (depends on 1)

The photodiode structure of claim 1, wherein the fill factor is at least 90%.

### Claim 5 (depends on 1)

The photodiode structure of claim 1, wherein each of the one or more absorber layers, the n-type layer, and the p-type layer are characterized by a crystallographic orientation within 5 degrees of (0001) +c-plane and each of the n-type and p-type layers are characterized by a dopant concentration of at least 1×1019 cm−3.

### Claim 6 (depends on 1)

The photodiode structure of claim 1, further comprising at least one of an n-type cladding layer and a p-type cladding layer, wherein
the n-type cladding layer lies between the n-type layer and the one or more absorber layers,
the n-type cladding layer has a dopant concentration of at least 5×1018 cm−3,
the p-type cladding layer lies between the one or more absorber layers and the p-type layer, and
the p-type cladding layer has a dopant concentration of at least 1×1019 cm−3.

### Claim 7 (depends on 1)

The photodiode structure of claim 1, further comprising:
at least one of an n-type cladding layer and a p-type cladding layer,
the n-type cladding layer lying between the n-type layer and the one or more absorber layers, and
the p-type cladding layer lying between the one or more absorber layers and the p-type layer,
wherein the at least one of the n-type cladding layer and the p-type cladding layer is characterized by an indium concentration intermediate between that of the one or more absorber layers and that of the n-type layer or p-type layer.

### Claim 8 (depends on 1)

The photodiode structure of claim 1, wherein each of the one or more absorber layers, the n-type layer, and the p-type layer are characterized by a crystallographic orientation that differs from (000-1) −c-plane by between 2 degrees and 5 degrees.

### Claim 9 (depends on 1)

The photodiode structure of claim 1, wherein each of the one or more absorber layers, the n-type layer, and the p-type layer are characterized by a crystallographic orientation within 5 degrees of {10-10} m-plane and each of the n-type and p-type layers are characterized by a dopant concentration of at least 2×1018 cm−3.

### Claim 10 (depends on 1)

The photodiode structure of claim 1, wherein each of the one or more absorber layers, the n-type layer, and the p-type layer are characterized by a crystallographic orientation within 5 degrees of a semipolar plane selected from {10-1-2}, {10-1-1}, {20-2-1}, and {30-3-1} and each of the n-type and p-type layers are characterized by a dopant concentration of at least 1×1018 cm−3.

### Claim 11 (depends on 1)

The photodiode structure of claim 1, wherein
the p-side electrical contact layer is disposed over the p-type layer, and
has an average reflectance of at least 80% for at least one wavelength between 390 nanometers and 460 nanometers and a contact resistance below 1×10−3 Ωcm2.

### Claim 12 (depends on 1)

The photodiode structure of claim 1, wherein the n-side electrical contact layer has an average reflectance of at least 80% for at least one wavelength between 390 nanometers and 460 nanometers and a contact resistance below 5×10−4 Ωcm2.

### Claim 13 (depends on 1)

The photodiode structure of claim 1, wherein each of the n-type layer, the one or more absorber layers, and the p-type layer have a threading dislocation density below 107 cm−2.

### Claim 14 (depends on 1)

The photodiode structure of claim 1, wherein each of the n-type layer, the one or more absorber layers, and the p-type layer have a threading dislocation density below 106 cm−2.

### Claim 15

A photodiode structure, comprising:
one or more absorber layers, wherein the one or more absorber layers comprise AlxInyGa1-x-yN, where 0≤x, y, x+y≤1;
an n-type layer and a p-type layer, wherein
the one or more absorber layers are disposed over the n-type layer,
the p-type layer is disposed over the one or more absorber layers, and
the n-type layer and the p-type layer each comprise AlxInyGa1-x-yN, where 0≤x, y, x+y≤1, and have a dopant concentration of at least 1×1016 cm−3;
a carrier substrate having a first surface and a second surface, wherein
the first surface of the carrier substrate is disposed over the p-type layer or under the n-type layer, and
the carrier substrate is substantially transparent at wavelengths between 390 nanometers and 460 nanometers;
a p-side electrical contact layer placed in electrical contact with the p-type layer, wherein the p-side electrical contact layer has a contact resistance below 3×10−3 Ωcm2;
a p-side reflector layer disposed on one of the p-type layer and the second surface of the carrier substrate, the p-side reflector layer having an average reflectance of at least 70% for at least one wavelength between 390 nanometers and 460 nanometers;
an n-side electrical contact layer placed in electrical contact with the n-type layer, wherein the n-side electrical contact layer has a contact resistance below 1×10−3 Ωcm2;
an n-side reflector layer disposed over one of an n-side layer and the second surface of the carrier substrate, the n-side reflector layer having an average reflectance of at least 70% for at least one wavelength between 390 nanometers and 460 nanometers; and
a light receiving surface, wherein the light receiving surface is aligned to cause light, having at least one wavelength between 390 nanometers and 460 nanometers and incident on the light receiving surface at an angle, to be reflected at least once from the n-side reflector layer and from the p-side reflector layer, wherein the photodiode structure is characterized by a fill factor of at least 50%.

### Claim 16 (depends on 15)

The photodiode structure of claim 15, wherein the fill factor is achieved under an illumination level producing a current density of at least 10 A cm−2.

### Claim 17 (depends on 15)

The photodiode structure of claim 15, wherein the fill factor is at least 80%.

### Claim 18 (depends on 15)

The photodiode structure of claim 15, wherein the fill factor is at least 90%.

### Claim 19 (depends on 15)

The photodiode structure of claim 15, wherein each of the one or more absorber layers, the n-type layer, and the p-type layer are characterized by a crystallographic orientation within 5 degrees of (0001) +c-plane and each of the n-type and p-type layers are characterized by a dopant concentration of at least 1×1019 cm−3.

### Claim 20 (depends on 15)

The photodiode structure of claim 15, further comprising at least one of an n-type cladding layer and a p-type cladding layer, wherein
the n-type cladding layer lies between the n-type layer and the one or more absorber layers,
the n-type cladding layer has a dopant concentration of at least 5×1018 cm−3,
the p-type cladding layer lies between the one or more absorber layers and the p-type layer, and
the p-type cladding layer has a dopant concentration of at least 1×1019 cm−3.

### Claim 21 (depends on 15)

The photodiode structure of claim 15, further comprising:
at least one of an n-type cladding layer and a p-type cladding layer,
the n-type cladding layer lying between the n-type layer and the one or more absorber layers, and
the p-type cladding layer lying between the one or more absorber layers and the p-type layer,
wherein the at least one of the n-type cladding layer and the p-type cladding layer is characterized by an indium concentration intermediate between that of the one or more absorber layers and that of the n-type layer or p-type layer.

### Claim 22 (depends on 15)

The photodiode structure of claim 15, wherein each of the one or more absorber layers, the n-type layer, and the p-type layer are characterized by a crystallographic orientation that differs from (000-1) −c-plane by between 2 degrees and 5 degrees.

### Claim 23 (depends on 15)

The photodiode structure of claim 15, wherein each of the one or more absorber layers, the n-type layer, and the p-type layer are characterized by a crystallographic orientation within 5 degrees of {10-10} m-plane and each of the n-type and p-type layers are characterized by a dopant concentration of at least 2×1018 cm−3.

### Claim 24 (depends on 15)

The photodiode structure of claim 15, wherein each of the one or more absorber layers, the n-type layer, and the p-type layer are characterized by a crystallographic orientation within 5 degrees of a semipolar plane selected from {10-1-2}, {10-1-1}, {20-2-1}, and {30-3-1} and each of the n-type and p-type layers are characterized by a dopant concentration of at least 1×1018 cm−3.

### Claim 25 (depends on 15)

The photodiode structure of claim 15, wherein the p-side electrical contact layer:
is disposed over the p-type layer, and
has an average reflectance of at least 80% for at least one wavelength between 390 nanometers and 460 nanometers and a contact resistance below 1×10−3 Ωcm2.

### Claim 26 (depends on 15)

The photodiode structure of claim 15, wherein the n-side electrical contact layer has an average reflectance of at least 80% for at least one wavelength between 390 nanometers and 460 nanometers and a contact resistance below 5×10−4 Ωcm2.