(Al,Ga,In)N diode laser fabricated at reduced temperature

• US 8,254,423 B2
• Filed: 06/01/2009
• Issued: 08/28/2012
• Est. Priority Date: 05/30/2008
• Status: Active Grant

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Cohen, Daniel A., DenBaars, Steven P., Nakamura, Shuji
• Primary Examiner(s): Stafford, Patrick
• Application Number:
  US12/476,208
• Publication Number:
  US 20100142576A1
• Time in Patent Office: 1,184 Days
• Field of Search: 372/45.01
• US Class Current: 372/45.01
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: H01L 21/02631 Physical deposition at reduced pressure, e.g. MBE, sputtering, evaporation
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01S 2304/04 MOCVD or MOVPE
• CPC Class Codes: H01S 2304/12 Pendeo epitaxial lateral overgrowth [ELOG], e.g. for growing GaN based blue laser diodes
• CPC Class Codes: H01S 5/0215 Bonding to the substrate
• CPC Class Codes: H01S 5/0217 Removal of the substrate
• CPC Class Codes: H01S 5/2009 by using electron barrier layers
• CPC Class Codes: H01S 5/2054 Methods of obtaining the confinement
• CPC Class Codes: H01S 5/22 having a ridge or stripe structure
• CPC Class Codes: H01S 5/3013 AIIIBV compounds
• CPC Class Codes: H01S 5/3211 characterised by special cladding layers, e.g. details on band-discontinuities
• CPC Class Codes: H01S 5/3213 asymmetric clading layers
• CPC Class Codes: H01S 5/3214 comprising materials from other groups of the periodic system than the materials of the active layer, e.g. ZnSe claddings and GaAs active layer
• CPC Class Codes: H01S 5/34333 with a well layer based on Ga(In)N or Ga(In)P, e.g. blue laser

Abstract

A method of fabricating an (Al,Ga,In)N laser diode, comprising depositing one or more III-N layers upon a growth substrate at a first temperature, depositing an indium containing laser core at a second temperature upon layers deposited at a first temperature, and performing all subsequent fabrication steps under conditions that inhibit degradation of the laser core, wherein the conditions are a substantially lower temperature than the second temperature.

Claims

1. An (Al,Ga,In)N based diode laser comprising:

(a) a plurality of (Al,Ga,In)N layers, including an indium-containing active region, for generating and confining green light having a laser wavelength longer than 515 nm; and

(b) at least one transparent and electrically conducting layer deposited on or above the indium-containing active region as a waveguide or cladding layer and to provide electrical contact to the indium-containing active region, wherein the transparent and electrically conducting layer comprises one or more oxide layers or bonded (Al,Ga,In)N layers, and the transparent and electrically conducting layer is deposited by a method other than crystal growth at a temperature above 550°

C. to prevent degradation of the indium-containing active region.

2. The (Al,Ga,In)N based diode laser of claim 1, wherein the transparent and electrically conducting layer is amorphous.

3. The (Al,Ga,In)N based diode laser of claim 1, wherein the transparent and electrically conducting layer is crystalline.

4. The (Al,Ga,In)N based diode laser of claim 1, wherein the transparent and electrically conducting layer is Indium Tin Oxide (ITO).

5. The (Al,Ga,In)N based diode laser of claim 1, wherein the transparent and electrically conducting layer is Zinc Oxide (ZnO).

6. The (Al,Ga,In)N based diode laser of claim 1, wherein the transparent and electrically conducting layer is selected from a group comprising metal oxides including tin oxide, zinc oxide, gallium oxide, magnesium oxide, cadmium oxide, and alloys of these compounds.

7. The (Al,Ga,In)N based diode laser of claim 1, wherein the transparent and electrically conducting layer is a III-N material wafer bonded to the (Al,Ga,In)N layers.

8. The (Al,Ga,In)N based diode laser of claim 1, wherein the transparent and electrically conducting layer is a cladding layer that improves confinement of light to the (Al,Ga,In)N layers.

9. The (Al,Ga,In)N based diode laser of claim 1, wherein the transparent and electrically conducting layer is different from a III-Nitride material.

10. The (Al,Ga,In)N based diode laser of claim 1, wherein the transparent and electrically conducting layer is patterned in a plane of the transparent and electrically conducting layer to form a rib or ridge, to serve as a lateral waveguide.

11. The (Al,Ga,In)N based diode laser of claim 1, further comprising a wafer bond between the transparent and electrically conducting layer and the (Al,Ga,In)N layers.

12. The (Al,Ga,In)N based diode laser of claim 1 wherein the transparent and electrically conducting layer, serving as an upper cladding layer, is a growth on the (Al,Ga,In)N layers.

13. The (Al,Ga,In)N based diode laser of claim 12, wherein the (Al,Ga,In)N layers are fabricated on a lower cladding layer, the effective refractive index of the (Al,Ga,In)N layers is higher than that of the lower cladding layer, and higher than that of the upper cladding layer, so that the (Al,Ga,In)N layers function as a transverse optical waveguide.

14. The (Al,Ga,In)N based diode laser of claim 1, wherein the (Al,Ga,In)N layers is deposited on a transparent layer of lower refractive index, such that the transparent layer of lower refractive index serves as a transverse optical waveguide cladding layer.

15. The (Al,Ga,In)N based diode laser of claim 1, wherein the (Al,Ga,In)N layers is patterned in a plane of the (Al,Ga,In)N layers to form a rib or ridge, to serve as a lateral waveguide.

16. The (Al,Ga,In)N based diode laser of claim 1, wherein the (Al,Ga,In)N layers comprises:

(a) the active region grown on a III-Nitride lower injection layer, wherein the III-Nitride lower injection layer serves to inject either electrons or holes into the active region,

(b) the active region comprising;

(1) at least one indium-containing active layer in which the light is generated; and

(2) III-Nitride confinement layers adjacent to each side of the active layer, serving to confine the electrons and holes;

(c) at least one III-Nitride upper injection layer grown on the active region, serving as an upper injection layer for carriers of a type not provided by the lower injection layer; and

(d) at least one first III-Nitride blocking layer between the active region and the lower injection layer, or at least one second III-Nitride blocking layer between the active region and the upper injection layer, or the first III-Nitride blocking layer and the second III-Nitride blocking layer, wherein;

(i) the first III-Nitride blocking layer serves to prevent injection of first minority carriers into the lower injection layer and the first minority carriers are carriers of the type not provided by the lower injection layer, and

(ii) the second III-Nitride blocking layer serves to prevent injection of second minority carriers into the upper injection layer and the second minority carriers are carriers of a type not provided by the upper injection layer.

24. The (Al,Ga,In)N based diode laser of claim 1, wherein the transparent and electrically conducting layer has a refractive index lower than an effective refractive index of the indium-containing active region.

25. The (Al,Ga,In)N based diode laser of claim 1, wherein the transparent and electrically conducting layer has a bulk resistivity below 10 Ohm-cm and is capable of making an electrical contact to the (Al,In,Ga) laser with a specific contact resistance below 0.01 Ohm-cm².

26. The (Al,Ga,In)N based diode laser of claim 1, wherein the transparent and electrically conducting layer has an optical absorption coefficient below 2000 cm⁻

1 measured at the laser wavelength.

17. A method of fabricating an (Al,Ga,In)N based diode laser comprising:

fabricating a plurality of (Al,Ga,In)N layers, including an indium-containing active region, for generating and confining green light having a laser wavelength longer than 515 nm; and

depositing at least one transparent and electrically conducting layer on or above the indium-containing active region as a waveguide or cladding layer and to provide electrical contact to the indium-containing active region, wherein the transparent and electrically conducting layer comprises one or more oxide layers or bonded (Al,Ga,In)N layers, and the transparent and electrically conducting layer is deposited by a method other than crystal growth at a temperature greater than 550°

C. to prevent degradation of the indium-containing active region.

18. The method of claim 17, wherein the indium-containing active region is fabricated by metal organic chemical vapor deposition (MOCVD).

19. The method of claim 17, wherein the transparent and electrically conducting layer is a crystalline transparent conductive oxide layer grown from an aqueous solution.

20. The method of claim 17, wherein the transparent and electrically conducting layer is a combination of a crystalline transparent conductive oxide layer grown from an aqueous solution and an amorphous or polycrystalline transparent conducting oxide layer deposited by physical vapor deposition.

21. The method of claim 17, wherein the transparent and electrically conducting layer is an amorphous or polycrystalline transparent conducting oxide formed by physical vapor deposition.

22. The method of claim 17, wherein the transparent and electrically conducting layer is a crystalline transparent conductive oxide layer wafer bonded to the (Al,Ga,In)N layers.

23. The method of claim 17, wherein the transparent and electrically conducting layer comprises (Al,Ga,In)N layers grown on a sacrificial substrate and wafer bonded to the (Al,Ga,In)N layers.