# US 10,121,819 B2 · Phototransistor having E-B junction and B-C junction are in direct physical contact and completely encapsulated only by the emitter, the collector and a dielectric

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- Number: US 10,121,819 B2
- Document ID: US10121819B2
- Status: Granted
- Kind: B2
- Application number: 15/372,950
- Filed: 2016-12-08
- Published: 2018-08-16
- Granted: 2018-11-06
- Earliest claimed: 2015-12-14
- Assignees: Wavefront Holdings, LLC
- Applicants: Wavefront Holdings, LLC
- Inventors: Jie Yao
- Web page: https://patentgrep.com/patent/US10121819B2

## CPC

- H10F 39/197: {Bipolar transistor image sensors}
- H10F 30/245: {Bipolar phototransistors}
- H10F 39/802: {Geometry or disposition of elements in pixels, e.g. address-lines or gate electrodes}
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION

## Abstract

Disclosed herein is a phototransistor (PT) comprising an emitter, a collector and a floating base; wherein the floating base, a p-n junction between the emitter and base (E-B junction) and a p-n junction between the base and the collector (B-C junction) are collectively in direct physical contact only with and completely encapsulated only by the emitter, the collector, and a section of a dielectric. Under an operating condition of the PT, a DC current density averaged over the E-B junction or a DC current density averaged over the B-C junction may be at least 100 times of a DC current density averaged over an opto-electronically active region of the PT. A sum of a capacitance of the E-B junction and a capacitance of the B-C junction may be less than 1 fF.

## Claims

### Claim 1

A phototransistor (PT) comprising an emitter, a collector and a floating base;
wherein the floating base, a p-n junction between the emitter and base (E-B junction) and a p-n junction between the base and the collector (B-C junction) are collectively in direct physical contact only with and completely encapsulated only by the emitter, the collector, and a section of a dielectric.

### Claim 2 (depends on 1)

The PT of claim 1, wherein the dielectric comprises dry thermal oxide, high-k dielectric, or a combination thereof.

### Claim 3 (depends on 1)

The PT of claim 1, wherein the section of the dielectric is planar.

### Claim 4 (depends on 1)

The PT of claim 1, wherein neither of the E-B junction and the C-B junction comprises a type-II hetero-structure.

### Claim 5 (depends on 1)

The PT of claim 1, wherein, under an operating condition of the PT, a direct-current (DC) current density averaged over the E-B junction is at least 100 times of a DC current density averaged over an opto-electronically active region of the PT, or a DC current density averaged over the B-C junction is at least 100 times of the DC current density averaged over the opto-electronically active region of the PT.

### Claim 6 (depends on 5)

The PT of claim 5, wherein the DC current density averaged over the E-B junction or the DC current density averaged over the B-C junction is at least 1000 times of the DC current density averaged over the opto-electronically active region of the PT.

### Claim 7 (depends on 1)

The PT of claim 1, wherein, under an operating condition of the PT, a sum of a capacitance of the E-B junction and a capacitance of the B-C junction is less than 1 fF.

### Claim 8 (depends on 7)

The PT of claim 7, wherein the sum is less than 0.1 fF.

### Claim 9 (depends on 1)

The PT of claim 1, wherein, under an operating condition of the PT, a depletion width of the E-B junction ora depletion width of the B-C junction exceeds 300 nm.

### Claim 10 (depends on 9)

The PT of claim 9, wherein the depletion width of the E-B junction or the depletion width of the B-C junction exceeds 1000 nm.

### Claim 11 (depends on 1)

The PT of claim 1, wherein, under an operating condition of the PT, an area of the E-B junction or an area of the B-C junction is less than 1/100 of an area of an opto-electronically active region of the PT.

### Claim 12 (depends on 11)

The PT of claim 11, wherein the area of the E-B junction or the area of the B-C junction is less than 1/1000 of the area of the opto-electronically active region of the PT.

### Claim 13 (depends on 1)

The PT of claim 1, wherein, under an operating condition of the PT, an area of the E-B junction or an area of the B-C junction is less than 1 μm2.

### Claim 14 (depends on 13)

The PT of claim 13, wherein the area of the E-B junction or the area of the B-C junction is less than 100000 nm2.

### Claim 15 (depends on 1)

The PT of claim 1, wherein, under an operating condition of the PT, a linear dimension of the E-B junction or a linear dimension of the B-C junction is less than 1/10 of a maximum linear dimension of an opto-electronically active region of the PT.

### Claim 16 (depends on 15)

The PT of claim 15, wherein the linear dimension of the E-B junction or the linear dimension of the B-C junction is less than 1/100 of the maximum linear dimension of the opto-electronically active region of the PT.

### Claim 17 (depends on 1)

The PT of claim 1, wherein, under an operating condition of the PT, a linear dimension of the E-B junction or a linear dimension of the B-C junction is less than 1 μm.

### Claim 18 (depends on 17)

The PT of claim 17, wherein the linear dimension of the E-B junction or the linear dimension of the B-C junction is less than 300 nm.

### Claim 19 (depends on 1)

The PT of claim 1, with at least half of an atomic composition in an opto-electronically active region of the PT being silicon, wherein the PT has a photo-response 3-dB bandwidth (f3dB) greater than 10 Hz in a limit of diminishing optical illumination, or wherein the PT has a transition frequency (fT) greater than 100 Hz in the limit of diminishing optical illumination, under an operating condition of the PT and at room temperature.

### Claim 20 (depends on 19)

The PT of claim 19, wherein the fT is greater than 1000 Hz.

### Claim 21 (depends on 1)

An apparatus comprising a PT of claim 1, wherein the apparatus is selected from a group consisting of a focal plane array (FPA), an optical receiver, a camera, an imager, a LIDAR (Light Detection and Ranging) and a combination thereof.