# US 2019/0378949 A1 · Optical semiconductor device and optical transceiver

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- Number: US 2019/0378949 A1
- Document ID: US20190378949A1
- Status: Published application
- Kind: A1
- Application number: 16/426,573
- Filed: 2019-05-30
- Published: 2019-12-12
- Earliest claimed: 2018-06-06
- Assignees: Fujitsu Limited; Photonics Electronics Technology Research Association
- Applicants: Fujitsu Limited; Photonics Electronics Technology Research Association
- Inventors: Takasi SIMOYAMA
- Web page: https://patentgrep.com/patent/US20190378949A1

## CPC

- H10F 10/17: Photovoltaic cells having only PIN junction potential barriers
- H10F 30/2255: {in which the active layers form heterostructures, e.g. SAM structures}
- H10F 30/223: the potential barrier being a PIN barrier
- H10F 30/225: the potential barrier working in avalanche mode, e.g. avalanche photodiodes
- Y02E 10/548: Amorphous silicon PV cells
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

A disclosed optical semiconductor device includes a first semiconductor layer having a first refractive index and a first optical absorption coefficient; and a second semiconductor layer formed on the first semiconductor layer, the second semiconductor layer having a second refractive index and a second optical absorption coefficient. The second refractive index is larger than the first refractive index, and the second optical absorption coefficient is larger than the first optical absorption coefficient. The first semiconductor layer includes a first region of p-type, a second region of n-type, a third region of p-type or n-type between the first region and the second region, a fourth region of i-type between the first region and the third region, and a fifth region of i-type between the second region and the third region. The second semiconductor layer is formed on the first region, the fourth region, and the third region.

## Claims

### Claim 1

An optical semiconductor device comprising:
a first semiconductor layer having a first refractive index and a first optical absorption coefficient; and
a second semiconductor layer formed on the first semiconductor layer, the second semiconductor layer having a second refractive index and a second optical absorption coefficient,
wherein the second refractive index is larger than the first refractive index, and the second optical absorption coefficient is larger than the first optical absorption coefficient,
wherein the first semiconductor layer includes
a first region of p-type,
a second region of n-type,
a third region of p-type or n-type between the first region and the second region,
a fourth region of i-type between the first region and the third region, and
a fifth region of i-type between the second region and the third region, and
wherein the second semiconductor layer is formed on the first region, the fourth region, and the third region.

### Claim 2 (depends on 1)

The optical semiconductor device as claimed in claim 1, further comprising:
a first metal film in ohmic contact with the first region; and
a second metal film in ohmic contact with the second region.

### Claim 3 (depends on 2)

The optical semiconductor device as claimed in claim 2, wherein
the first region includes
a sixth region in contact with the first metal film, and
a seventh region in contact with the fourth region, wherein
the sixth region includes a p-type dopant at a higher concentration than the seventh region.

### Claim 4 (depends on 1)

The optical semiconductor device as claimed in claim 1, wherein
the third region is n-type, and
the second region includes an n-type dopant at a higher concentration than the third region.

### Claim 5 (depends on 1)

The optical semiconductor device as claimed in claim 1, wherein
a recess is formed in a region where the first semiconductor layer is in contact with the second semiconductor layer.

### Claim 6 (depends on 1)

The optical semiconductor device as claimed in claim 1, further comprising:
an opto-electric converter including the first semiconductor layer and the second semiconductor layer that overlap each other in a plane view,
a mode converter connected to the opto-electric converter, wherein
in the mode converter, the first semiconductor layer has a planar shape having a width that increases toward the opto-electric converter.

### Claim 7 (depends on 1)

The optical semiconductor device as claimed in claim 1, wherein
the first semiconductor layer is a Si layer, and
the second semiconductor layer is a SixGe1-x layer (0≤x<1).

### Claim 8 (depends on 1)

The optical semiconductor device as claimed in claim 1, wherein
the first semiconductor layer is a Si layer, and
the second semiconductor layer is a Ge1-xSnx layer (0≤x<1).

### Claim 9 (depends on 1)

An optical transceiver comprising:
the optical semiconductor device as claimed in claim 1.