Nitride semiconductor vertical cavity surface emitting laser

• US 20070036186A1
• Filed: 08/15/2005
• Published: 02/15/2007
• Est. Priority Date: 08/15/2005
• Status: Active Grant

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Avago Technologies ECBU IP Singapore Pte Limited (Broadcom, Inc.)
• Inventors: Bour, David, Corzine, Scott
• Granted Patent: US 7,352,788 B2
• Time in Patent Office: Days
• US Class Current: 372/50.110
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: H01S 2304/12 Pendeo epitaxial lateral overgrowth [ELOG], e.g. for growing GaN based blue laser diodes
• CPC Class Codes: H01S 5/0424 lateral current injection
• CPC Class Codes: H01S 5/18341 Intra-cavity contacts
• CPC Class Codes: H01S 5/18369 based on dielectric materials
• CPC Class Codes: H01S 5/18383 with periodic active regions at nodes or maxima of light intensity
• CPC Class Codes: H01S 5/20 Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
• CPC Class Codes: H01S 5/34333 with a well layer based on Ga(In)N or Ga(In)P, e.g. blue laser

Abstract

In one aspect, a VCSEL includes a base region that has a vertical growth part laterally adjacent a first optical reflector and a lateral growth part that includes nitride semiconductor material vertically over at least a portion of the first optical reflector. An active region has at least one nitride semiconductor quantum well vertically over at least a portion of the lateral growth part of the base region and includes a first dopant of a first electrical conductivity type. A contact region includes a nitride semiconductor material laterally adjacent the active region and a second dopant of a second electrical conductivity type opposite the first electrical conductivity type. A second optical reflector is vertically over the active region and forms with the first optical reflector a vertical optical cavity overlapping at least a portion of the at least one quantum well of the active region. A method of fabricating a VCSEL also is described.

Claims

1. A vertical cavity surface emitting laser (VCSEL), comprising:

a first optical reflector;

a base region having a vertical growth part laterally adjacent the first optical reflector and a lateral growth part comprising a nitride semiconductor material vertically over at least a portion of the first optical reflector;

an active region having at least one nitride semiconductor quantum well vertically over at least a portion of the lateral growth part of the base region, the active region comprising a first dopant of a first electrical conductivity type;

a contact region comprising a nitride semiconductor material laterally adjacent the active region and a second dopant of a second electrical conductivity type opposite the first electrical conductivity type; and

a second optical reflector vertically over the active region and forming with the first optical reflector a vertical optical cavity vertically overlapping at least a portion of the at least one quantum well of the active region.

2. The VCSEL of claim 1, wherein the base region is formed of Al_xIn_yGa_1-x-yN, where 0≦

x,y≦

1 and 0≦

x+y≦

1.

3. The VCSEL of claim 2, wherein the base region is formed of GaN.

4. The VCSEL of claim 1, wherein the contact region is formed of Al_xIn_yGa_1-x-yN, where 0≦

x,y≦

1 and 0≦

x+y≦

1.

5. The VCSEL of claim 4, wherein the contact region is formed of GaN.

6. The VCSEL of claim 1, wherein the first dopant is an n-type dopant and the second dopant is a p-type dopant.

7. The VCSEL of claim 1, wherein the active region comprises a quantum well layer between a pair of barrier layers, each of the quantum well and barrier layers being formed of respective nitride semiconductor material selected from Al_xIn_yGa_1-x-yN, where 0≦

x,y≦

1 and 0≦

x+y≦

1.

8. The VCSEL of claim 7, wherein the barrier layers are formed of GaN, and the quantum well layer is formed of InGaN.

9. The VCSEL of claim 7, wherein the barrier layers are doped with the first dopant.

10. The VCSEL of claim 9, wherein the quantum well layer is doped with the first dopant.

11. The VCSEL of claim 1, further comprising a first electrode forming an ohmic contact with the contact region.

12. The VCSEL of claim 11, further comprising a second electrode forming an ohmic contact with the active region.

13. The VCSEL of claim 11, further comprising a second electrode electrically connected to the active region through the base region.

14. The VCSEL of claim 1, wherein the at least one quantum well substantially coincides with a peak in a standing optical wave having a specified optical wavelength in the vertical optical cavity.

15. A vertical cavity surface emitting laser (VCSEL), comprising:

a first distributed Bragg reflector;

a GaN base region having a vertical growth part laterally adjacent the first optical reflector and a lateral growth part vertically over at least a portion of the first optical reflector;

an active region vertically over at least a portion of the lateral growth part of the base region and comprising an n-type dopant, wherein the active region comprises a quantum well layer between a pair of barrier layers, each of the quantum well and barrier layers being formed of respective nitride semiconductor material selected from Al_xIn_yGa_1-x-yN, where 0≦

x,y≦

1 and 0≦

x+y≦

1;

a GaN contact region laterally adjacent the active region and comprising a p-type dopant; and

a second distributed Bragg reflector vertically over the active region and defining with the first optical reflector a vertical optical cavity overlapping at least a portion of the at least one quantum well of the active region.

16. A method of fabricating a vertical cavity surface emitting laser (VCSEL), comprising:

forming a first optical reflector;

forming a base region having a vertical growth part laterally adjacent the first optical reflector and a lateral growth part comprising a nitride semiconductor material vertically over at least a portion of the first optical reflector;

forming an active region having at least one nitride semiconductor quantum well vertically over at least a portion of the lateral growth part of the base region, the active region comprising a first dopant of a first electrical conductivity type;

forming a contact region comprising a nitride semiconductor material laterally adjacent the active region and a second dopant of a second electrical conductivity type opposite the first electrical conductivity type; and

forming a second optical reflector over the active region, wherein the first and second optical reflectors form a vertical optical cavity vertically overlapping at least a portion of the at least one quantum well of the active region.

17. The method of claim 16, wherein the base region is formed of Al_xIn_yGa_1-x-yN, where 0≦

x,y≦

1 and 0≦

x+y≦

1.

18. The method of claim 16, wherein the contact region is formed of Al_xIn_yGa_1-x-yN, where 0≦

x,y≦

1 and 0≦

x+y≦

1.

19. The method of claim 16, wherein the first dopant is an n-type dopant and the second dopant is a p-type dopant.

20. The method of claim 16, wherein the active region comprises a quantum well layer between a pair of barrier layers, each of the quantum well and barrier layers being formed of respective nitride semiconductor material selected from Al_xIn_yGa_1-x-yN, where 0≦

x,y≦

1 and 0≦

x+y≦

1.

21. The method of claim 16, wherein the forming of the contact region comprises laterally growing epitaxial nitride semiconductor material from the active region.