Quantum-well type semiconductor laser device having multi-layered quantum-well layer

• US 5,642,372 A
• Filed: 12/27/1994
• Issued: 06/24/1997
• Est. Priority Date: 12/27/1993
• Status: Expired due to Fees

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Tomita, Akihisa
• Primary Examiner(s): Davie, James W.
• Application Number:
  US08/364,269
• Time in Patent Office: 910 Days
• Field of Search: 372/45, 372/46, 372/44
• US Class Current: 372/45.01
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: H01S 5/2004 Confining in the direction perpendicular to the layer structure
• CPC Class Codes: H01S 5/2009 by using electron barrier layers
• CPC Class Codes: H01S 5/34 comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers H01S5/36 takes precedence
• CPC Class Codes: H01S 5/3407 characterised by special barrier layers
• CPC Class Codes: H01S 5/3415 containing details related to carrier capture times into wells or barriers
• CPC Class Codes: H01S 5/3416 tunneling through barriers
• CPC Class Codes: H01S 5/34306 emitting light at a wavelength longer than 1000nm, e.g. InP based 1300 and 1500nm lasers
• CPC Class Codes: H01S 5/34313 with a well layer having only As as V-compound, e.g. AlGaAs, InGaAs
• CPC Class Codes: H01S 5/3434 with a well layer comprising at least both As and P as V-compounds

Abstract

The present invention provides a quantum-well semiconductor laser device having a substrate, a clad layer on the substrate, an optical confinement layer on the clad layer, an active layer on the optical confinement layer, an optical confinement layer on the active layer and a clad layer on the optical confinement layer each of which formed of a semiconductor wherein the active layer formed of a multi-layer quantum-well structure of which each layer comprising a quantum-well layer, a first barrier layer adjacent the quantum-well layer and a second barrier layer adjacent the first barrier layer wherein the semiconductor of the first barrier has a higher energy level at a Γ point of a valence band than that of the second barrier layer.

Claims

1. A quantum-well semiconductor laser device having a substrate, a clad layer on the substrate, an optical confinement layer on the clad layer, an active layer on the optical confinement layer, an optical confinement layer on the active layer and a clad layer on the optical confinement layer each of which formed on a semiconductor wherein the active layer formed of a multi-layer quantum-well structure of which each layer comprising a quantum-well layer, a first barrier layer adjacent the quantum-well layer and a second barrier layer adjacent the first barrier layer wherein the semiconductor of the first barrier has a higher energy level at a Γ

point of a valence band than a energy level at a Γ

point of a valence band of the second barrier layer.

2. A quantum-well semiconductor laser device as claimed in claim 1;

wherein the semiconductor of the quantum-well layer has the same lattice parameters as the semiconductor of the substrate.

3. A quantum-well semiconductor laser device as claimed in claim 1;

wherein the semiconductor of the quantum-well layer has lattice parameters different from those of the semiconductor of the substrate.

4. A quantum-well semiconductor laser device as claimed in claim 1;

wherein the first barrier layer has a thickness of from 1 to 5 nanometers.

5. A quantum-well semiconductor laser device as claimed in claim 4;

wherein difference between energy levels at the Γ

points of the valence bands of the semiconductors of the first and second barrier layers ranges from 20 to 150 meV.

6. A quantum-well semiconductor laser device as claimed in claim 4;

wherein the energy level at the Γ

point of the valence band of the semiconductor of the first barrier layer is between the lowest energy level of positive holes in the quantum-well layer and the energy level at the Γ

point of the valence band of the semiconductor of the second barrier layer.

7. A quantum-well semiconductor laser device as claimed in claim 6;

wherein the second barrier layer has a thickness of from 2 to 10 nanometers.

8. A quantum-well semiconductor laser device comprising:

an active layer formed of a plurality of multi-layered quantum-well structures, each having a well layer, a first barrier adjacent said well layer, and a second barrier layer adjacent said first barrier layer; and

wherein the semiconductor of the first barrier has a higher energy level at a Γ

point of a valence band than a energy level at a Γ

point of a valence band of the second barrier layer.

9. A quantum-well semiconductor laser device as claimed in claim 8;

wherein the first barrier layer has a thickness of from 1 to 5 nanometers.

10. A quantum-well semiconductor laser device as claimed in claim 9;

wherein the energy level at the Γ

point of the valence band of the semiconductor of the first barrier layer is between the lowest energy level of positive holes in the quantum-well layer and the energy level at the Γ

point of the valence band of the semiconductor of the second barrier layer.

11. A quantum-well semiconductor laser device as claimed in claim 9;

wherein the second barrier layer has a thickness of from 2 to 10 nanometers.

12. A quantum-well semiconductor laser device as claimed in claim 11;

wherein the difference between energy levels at the Γ

points of the valence bands of the semiconductors of the first and second barrier layers ranges from 20 to 150 meV.

13. A quantum-well semiconductor laser device as claimed in claim 12;

wherein the first barrier layer is made of non-doped InGaAsP having a band gap wavelength of from 0.98 μ

m to 1.6 μ

m.

14. A quantum-well semiconductor laser device as claimed in claim 13;

wherein the second barrier layer is made of non-doped InP.

15. A quantum-well semiconductor laser device as claimed in claim 14;

wherein the well layer is made of InGaAs having a thickness of from 2.3 to 7 nanometers.

16. A quantum-well semiconductor laser device comprising:

an active layer formed of a plurality of multi-layered quantum-well structures, each having a well layer, a first barrier adjacent said well layer, and a second barrier layer adjacent said first barrier layer; and

means for increasing the permeability of positive holes between said well layers of adjacent quantum-well structures in said active layer.

17. A quantum-well semiconductor laser device as claimed in claim 16, further comprising:

a substrate;

a first clad layer formed on a first surface of said substrate;

a first optical confinement layer formed on said first clad layer with said active layer formed thereon;

a second optical confinement layer formed on said active layer;

a second clad layer formed on said second optical confinement layer;

a contact layer formed on said second clad layer;

a first electrode formed on said contact layer; and

a second electrode formed on a second surface of said substrate.