Method of making a vertical cavity laser

• US 5,877,038 A
• Filed: 11/27/1996
• Issued: 03/02/1999
• Est. Priority Date: 11/27/1996
• Status: Expired due to Term

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: DenBaars, Steven P., Coldren, Larry A.
• Primary Examiner(s): DUTTON, BRIAN KEITH
• Application Number:
  US08/758,241
• Time in Patent Office: 825 Days
• Field of Search: 438/32, 438/39, 438/40, 438/41
• US Class Current: 438/39
• CPC Class Codes: H01S 5/18316 Airgap confined
• CPC Class Codes: H01S 5/18341 Intra-cavity contacts
• CPC Class Codes: H01S 5/18369 based on dielectric materials
• CPC Class Codes: H01S 5/1838 Reflector bonded by wafer fusion or by an intermediate compound
• CPC Class Codes: H01S 5/2086 lateral etch control, e.g. mask induced

Abstract

A highly controllable, compact method for making a vertical cavity laser. By using selective etching and contact layers within the laser cavity, higher efficiencies and lower power requirements for vertical cavity surface emitting lasers (VCSELs) are achieved.

Claims

1. A method of making a vertical cavity laser, comprising the step of forming at least one contact within the laser cavity, wherein the contact is positioned between a first mirror and a second mirror of the vertical cavity laser, and an active layer of the vertical cavity laser is a group III nitride film.

2. The method of claim 1, wherein the at least one contact is substantially transparent at a laser output frequency.

3. The method of claim 1, wherein the at least one contact layer is selected from a group comprising n+ doped gallium nitride, conducting indium tin oxide, and alloys of gallium nitride.

4. A method for making a vertical cavity laser, comprising the steps of:

growing a first mirror on a substrate;

growing a first contact layer on the first mirror;

growing an active layer on the first contact layer;

growing a second contact layer on the active layer;

growing a second mirror on the second contact layer;

undercutting the active layer to a first width;

etching the second mirror to a second width, such that the second width of the second mirror is wider than the first width and coaxial with the first width; and

etching the second contact layer to a third width, wherein the third width is wider than the second width and is offset from the axis of the first and second widths, and an edge of the second contact layer is flush with an edge of the second mirror.

5. The method of claim 4, wherein the first mirror is a distributed Bragg reflector.

6. The method of claim 4, wherein the second mirror is a distributed Bragg reflector.

7. The method of claim 4, wherein the first mirror is alternating layers of gallium nitride and aluminum nitride.

8. The method of claim 4, wherein the first contact is n+ doped gallium nitride.

9. The method of claim 4, wherein the second contact is p+ doped gallium nitride.

10. The method of claim 4, wherein the substrate is selected from a group comprising sapphire, silicon, silicon carbide, gallium nitride, and Al_x Ga_1-x N.

11. The method of claim 4, wherein the first contact layer is substantially transparent at a laser output frequency.

12. The method of claim 4, wherein the second contact layer is substantially transparent at a laser output frequency.

13. The method of claim 4, further comprising the steps of growing an inhibitor layer on the substrate, etching the inhibitor layer, such that the inhibitor layer contains apertures, the apertures exposing the substrate therein;

and growing the first mirror on the substrate within the apertures.

14. The method of claim 13, wherein the inhibitor layer is selected from a group comprising silicon dioxide, silicon nitride, and titanium dioxide.

15. A method for making a vertical cavity laser, comprising the steps of:

growing a first inhibitor layer on a substrate;

etching the first inhibitor layer, such that the first inhibitor layer contains apertures, the apertures exposing the substrate therein;

growing a first mirror on the substrate within the apertures;

growing a first contact layer on the first mirror;

growing an active layer on the first contact layer;

etching the active layer to a first width;

growing a second growth inhibitor on a first portion of the first contact layer and the proximate portion of the first inhibitor layer, such that the second growth inhibitor is adjacent to at least a portion of the active layer and such that a second portion of the first contact layer remains exposed;

etching the second portion of the first contact layer to a second width, such that the active layer overhangs at least part of the first contact layer, and whereby a portion of the first mirror is exposed;

growing a second contact layer on the active layer and the exposed portion of the first mirror;

growing a third inhibitor layer on the first inhibitor layer and on a portion of the second contact layer, whereby covering the portion of the second contact layer that overlays the first mirror;

growing a second mirror on a portion of the second contact layer not covered by the third inhibitor layer; and

etching the second and the third inhibitor layers to expose the first and second contact layers.

16. The method of claim 15, wherein the first inhibitor layer is selected from a group comprising silicon dioxide, silicon nitride, and titanium dioxide.

17. The method of claim 15, wherein the second inhibitor layer is selected from a group comprising silicon dioxide, silicon nitride, and titanium dioxide.

18. The method of claim 15, wherein the third inhibitor layer is selected from a group comprising silicon dioxide, silicon nitride, and titanium dioxide.

19. The method of claim 15, wherein a composition of a second mirror is selected from a group comprising insulating titanium dioxide/silicon oxide, magnesium fluoride/zinc sulfide, calcium fluoride/zinc sulfide, and conductive indium tin oxide/zinc oxide.

20. A method for making a vertical cavity laser, comprising the steps of:

growing a liftoff layer on a first substrate;

growing a first contact layer on the liftoff layer;

growing an active layer on the first contact layer;

growing a second contact layer on the active layer;

growing a first mirror on a second substrate;

growing a third contact layer on the first mirror;

bonding the second contact layer to the third contact layer;

removing the first substrate and liftoff layer from the first contact layer, thereby exposing the first contact layer;

depositing a second mirror on the first contact layer;

etching the second mirror to a first width; and

etching the first contact layer, active layer, second contact layer, and third contact layer to a second width, an axis of the second width being offset with an axis of the first width, such that the first width is offset coaxially from the second width.

21. The method of claim 20, where the liftoff layer is selected from a group comprising In_x Ga_y N, where x is less than 0.2, zinc oxide, lanthanum gallium oxide, silicon, and gallium arsenide.

22. The method of claim 20, where the first substrate is selected from a group comprising sapphire, silicon, gallium nitride, silicon carbide, and Al_x Ga_1-x N.

23. The method of claim 20, where the active layer is indium gallium nitride.

24. The method of claim 20, where the first mirror is alternating layers of aluminum gallium arsenide and oxidized aluminum arsenide.

25. The method of claim 20, where the third contact layer is partially oxidized p+ aluminum gallium arsenide.

26. The method of claim 20, where the step of bonding is done by fusion.

27. The method of claim 20, wherein the step of bonding is performed with an optically transparent material, selected from a group comprising epoxy bonding and optical cementing.

28. A method for making a vertical cavity laser, comprising the steps of:

growing a liftoff layer on a first substrate;

growing a first contact layer on the liftoff layer;

growing an active layer on the first contact layer;

growing a second contact layer on the active layer;

growing a first mirror on the second contact layer;

bonding the first mirror to a second substrate;

removing the first substrate and the liftoff layer from the first contact layer, thereby exposing the first contact layer;

depositing a second mirror on the exposed first contact layer; and

etching the second mirror to a first width; and

etching the first contact layer, active layer, and second contact layer to a second width, an axis of the second width being offset with an axis of the first width, such that the first width is offset coaxially from the second width.

29. The method of claim 28, wherein the first mirror is selected from a group comprising alternating layers of titanium oxide and silicon oxide, alternating layers of magnesium fluoride and zinc sulfide, alternating layers of calcium fluoride and zinc sulfide, and alternating layers of conductive indium tin oxide and zinc oxide.

30. The method of claim 28, wherein the method further comprises the step of attaching a backing layer to the first mirror for increasing a reflectivity of the first mirror.

31. The method of claim 28, wherein the method further comprises the step of attaching a backing layer to the second mirror for increasing a reflectivity of the second mirror.

32. The method of claim 28, wherein the step of bonding is performed with an optically transparent material, selected from a group comprising epoxy bonding optical cementing, and wafer fusing.