# US 10,312,665 B2 · Optical semiconductor device, optical subassembly, and optical module

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- Number: US 10,312,665 B2
- Document ID: US10312665B2
- Status: Granted
- Kind: B2
- Application number: 15/996,562
- Filed: 2018-06-04
- Published: 2018-12-20
- Granted: 2019-06-04
- Earliest claimed: 2017-06-14
- Assignees: Oclaro Japan, Inc.
- Applicants: Oclaro Japan, Inc.
- Inventors: Takeshi Kitatani; Kaoru Okamoto; Kouji Nakahara
- Web page: https://patentgrep.com/patent/US10312665B2

## CPC

- H01S 5/3218: {specially strained cladding layers, other than for strain compensation}
- H01S 5/0014: {Measuring characteristics or properties thereof (measuring techniques per se G01J, G01K, G01N, G01R)}
- H01S 5/0208: {Semi-insulating substrates}
- H01S 5/026: Monolithically integrated components, e.g. waveguides, monitoring photo-detectors, drivers (stabilisation of output H01S5/06)
- H01S 5/12: the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers (comprising a photonic bandgap structure H01S5/11; surface-emitting lasers H01S5/18)
- H01S 5/22: having a ridge or stripe structure
- H01S 5/305: {characterised by the doping materials used in the laser structure}
- H01S 5/3054: {p-doping}
- H01S 5/3063: {using Mg}
- H01S 5/3072: {Diffusion blocking layer, i.e. a special layer blocking diffusion of dopants}
- H01S 5/3201: {incorporating bulkstrain effects, e.g. strain compensation, strain related to polarisation}
- H01S 5/3211: {characterised by special cladding layers, e.g. details on band-discontinuities}
- H01S 5/3403: {having a strained layer structure in which the strain performs a special function, e.g. general strain effects, strain versus polarisation}
- H01S 5/343: in AIIIBV compounds, e.g. AlGaAs-laser {, InP-based laser}
- H01S 5/3432: {the whole junction comprising only (AI)GaAs}
- H01S 5/34366: {based on InGa(Al)AS}
- H10F 30/223: the potential barrier being a PIN barrier
- H10F 30/225: the potential barrier working in avalanche mode, e.g. avalanche photodiodes
- H10F 77/1248: {having three or more elements, e.g. GaAlAs, InGaAs or InGaAsP}
- H10F 77/14: Shape of semiconductor bodies; Shapes, relative sizes or dispositions of semiconductor regions within semiconductor bodies
- H10F 77/16: Material structures, e.g. crystalline structures, film structures or crystal plane orientations
- H01S 5/0265: {Intensity modulators (intra-cavity modulators H01S5/0625)}
- H01S 5/34306: {emitting light at a wavelength longer than 1000nm, e.g. InP based 1300 and 1500nm lasers}
- H01S 2301/173: The laser chip comprising special buffer layers, e.g. dislocation prevention or reduction
- H01S 2301/176: Specific passivation layers on surfaces other than the emission facet
- H01S 2304/04: MOCVD or MOVPE
- H01S: DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION

## Abstract

An optical semiconductor device includes an InP substrate; an active layer disposed above the InP substrate; a n-type semiconductor layer disposed below the active layer; and a p-type clad layer disposed above the active layer, wherein the p-type clad layer includes one or more p-type In1-xAlxP layers, the Al composition x of each of the one or more p-type In1-xAlxP layers is equal to or greater than a value corresponding to the doping concentration of a p-type dopant, and the absolute value of the average strain amount of the whole of the p-type clad layer is equal to or less than the absolute value of a critical strain amount obtained by Matthews' relational expression, using the entire layer thickness of the whole of the p-type clad layer as a critical layer thickness.

## Claims

### Claim 1

An optical semiconductor device, comprising:
an InP substrate;
an active layer disposed above the InP substrate;
a semiconductor layer of a first conductivity type disposed below the active layer; and
a clad layer of a second conductivity type disposed above the active layer, wherein
the clad layer of the second conductivity type includes one or more In1-xAlxP layers of the second conductivity type,
an Al composition x of each of the one or more In1-xAlxP layers of the second conductivity type is equal to or greater than a value corresponding to a doping concentration of a dopant of the second conductivity type, and
an absolute value of an average strain amount of a whole of the clad layer of the second conductivity type is equal to or less than an absolute value of a critical strain amount obtained by Matthews' relational expression, using an entire layer thickness of the whole of the clad layer of the second conductivity type as a critical layer thickness.

### Claim 2 (depends on 1)

The optical semiconductor device according to claim 1, wherein
the clad layer of the second conductivity type includes one In1-xAlxP layer of the second conductivity type,
an Al composition x of the one In1-xAlxP layer of the second conductivity type is equal to or greater than a value corresponding to a doping concentration of the dopant of the second conductivity type in the one In1-xAlxP layer of the second conductivity type, and
an absolute value of a strain amount of the one In1-xAlxP layer of the second conductivity type is equal to or less than an absolute value of a critical strain amount obtained by the Matthews' relational expression, using a layer thickness of the one In1-xAlxP layer of the second conductivity type as the critical layer thickness.

### Claim 3 (depends on 1)

The optical semiconductor device according to claim 1, wherein
the clad layer of the second conductivity type includes one InP layer of the second conductivity type and one In1-xAlxP layer of the second conductivity type,
an Al composition x of the one In1-xAlxP layer of the second conductivity type is equal to or greater than a value corresponding to a doping concentration of the dopant of the second conductivity type in the one In1-xAlxP layer of the second conductivity type, and
an absolute value of a strain amount of the one In1-xAlxP layer of the second conductivity type is equal to or less than an absolute value of a strain amount of the one In1-xAlxP layer of the second conductivity type, the strain amount being obtained based on an average strain amount of the whole of the clad layer of the second conductivity type, the average strain amount being a critical strain amount obtained by Matthews' relational expression, using the entire layer thickness of the whole of the clad layer of the second conductivity type as the critical layer thickness.

### Claim 4 (depends on 1)

The optical semiconductor device according to claim 1, wherein the clad layer of the second conductivity type includes an n (n being an integer equal to or greater than two) number of the In1-xAlxP layers of the second conductivity type and an (n−1) number of InP layers of the second conductivity type each being disposed between adjacent In1-xAlxP layers of the second conductivity type of the n number of the In1-xAlxP layers.

### Claim 5 (depends on 1)

The optical semiconductor device according to claim 1, wherein
the optical semiconductor device is a semiconductor light-emitting element,
the InP substrate is an InP substrate of the first conductivity type, and
the layer thickness of the whole of the clad layer of the second conductivity type is equal to or greater than 0.5 μm and equal to or less than 2 μm.

### Claim 6 (depends on 5)

The optical semiconductor device according to claim 5, further comprising a grating layer disposed between the active layer and the clad layer of the second conductivity type.

### Claim 7 (depends on 1)

The optical semiconductor device according to claim 1, wherein
the optical semiconductor device is a semiconductor optical modulator,
the InP substrate is an InP substrate of the first conductivity type, and
the layer thickness of the whole of the clad layer of the second conductivity type is equal to or greater than 0.5 μm and equal to or less than 2 μm.

### Claim 8 (depends on 1)

The optical semiconductor device according to claim 1, wherein
the optical semiconductor device is a semiconductor light-receiving element,
the InP substrate is a semi-insulating InP substrate, and
the layer thickness of the whole of the clad layer of the second conductivity type is equal to or greater than 0.5 μm and equal to or less than 2 μm.

### Claim 9 (depends on 1)

The optical semiconductor device according to claim 1, wherein
the first conductivity type is an n-type,
the second conductivity type is a p-type, and
the dopant of the second conductivity type is one or more atoms selected from a group consisting of Zn, Mg, and Be.

### Claim 10 (depends on 1)

An optical subassembly comprising the optical semiconductor device according to claim 1.

### Claim 11 (depends on 10)

An optical module comprising the optical subassembly according to claim 10.