# US 11,114,494 B2 · Image sensor based on avalanche photodiodes

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- Number: US 11,114,494 B2
- Document ID: US11114494B2
- Status: Granted
- Kind: B2
- Application number: 16/941,665
- Filed: 2020-07-29
- Published: 2020-11-12
- Granted: 2021-09-07
- Earliest claimed: 2016-06-21
- Assignees: Shenzhen Xpectvision Technology Co., Ltd.
- Applicants: Shenzhen Xpectvision Technology Co., Ltd.
- Inventors: Peiyan Cao; Yurun Liu
- Web page: https://patentgrep.com/patent/US11114494B2

## CPC

- H10F 39/18: Complementary metal-oxide-semiconductor [CMOS] image sensors; Photodiode array image sensors
- H10F 30/225: the potential barrier working in avalanche mode, e.g. avalanche photodiodes
- H10F 30/2255: {in which the active layers form heterostructures, e.g. SAM structures}
- H10F 39/802: {Geometry or disposition of elements in pixels, e.g. address-lines or gate electrodes}
- H10F 39/803: {Pixels having integrated switching, control, storage or amplification elements}
- G02B 21/361: {Optical details, e.g. image relay to the camera or image sensor (G02B21/364 takes precedence; illumination details G02B21/06 and subgroups)}
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

Disclosed herein is an apparatus comprising: an array of avalanche photodiodes (APDs), each of the APDs comprising an absorption region and an amplification region; wherein the absorption region is configured to generate charge carriers from a photon absorbed by the absorption region; wherein the absorption region comprises a silicon epitaxial layer; wherein the amplification region comprises a junction with an electric field in the junction; wherein the electric field is at a value sufficient to cause an avalanche of charge carriers entering the amplification region, but not sufficient to make the avalanche self-sustaining; wherein the junctions of the APDs are discrete.

## Claims

### Claim 1

An apparatus comprising:
an array of avalanche photodiodes (APDs), each of the APDs comprising an absorption region and an amplification region;
wherein the absorption region is configured to generate charge carriers from a photon absorbed by the absorption region;
wherein the absorption region comprises a silicon epitaxial layer;
wherein the amplification region comprises a junction with an electric field in the junction;
wherein the electric field is at a value sufficient to cause an avalanche of charge carriers entering the amplification region, but not sufficient to make the avalanche self-sustaining;
wherein the junctions of the APDs are discrete.

### Claim 2 (depends on 1)

The apparatus of claim 1, wherein an electric field in the absorption region is not high enough to cause avalanche effect in the absorption region.

### Claim 3 (depends on 1)

The apparatus of claim 1, wherein the silicon epitaxial layer has a doping level less than 1012 dopants/cm3.

### Claim 4 (depends on 1)

The apparatus of claim 1, wherein the absorption regions of at least some of the APDs are joined together.

### Claim 5 (depends on 1)

The apparatus of claim 1, wherein the amplification regions of the APDs are discrete.

### Claim 6 (depends on 1)

The apparatus of claim 1, wherein the junction is a p-n junction or a heterojunction.

### Claim 7 (depends on 1)

The apparatus of claim 1, wherein the junction comprises a first layer and a second layer, wherein the first layer is the silicon epitaxial layer and the second layer is a heavily doped semiconductor.

### Claim 8 (depends on 7)

The apparatus of claim 7, wherein the first layer has a doping level of 1013 to 1017 dopants/cm3.

### Claim 9 (depends on 7)

The apparatus of claim 7, wherein the first layers of least some of the APDs are joined together.

### Claim 10 (depends on 7)

The apparatus of claim 7, further comprising electrodes respectively in electrical contact with the second layers of the APDs.

### Claim 11 (depends on 1)

The apparatus of claim 1, further comprising a passivation material configured to passivate a surface of the absorption region.

### Claim 12 (depends on 1)

The apparatus of claim 1, further comprising a common electrode electrically connected to the absorption region.

### Claim 13 (depends on 1)

The apparatus of claim 1, wherein the junction is separated from a junction of a neighbor junction by a material of the absorption region.

### Claim 14 (depends on 1)

An apparatus comprising the apparatus of claim 1, wherein the system is configured to form an image of an object.