Group III-nitride layers with patterned surfaces

• US 20040189173A1
• Filed: 03/26/2003
• Published: 09/30/2004
• Est. Priority Date: 03/26/2003
• Status: Active Grant

• Current Assignee: Alcatel-Lucent SA (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Chowdhury, Aref, Ng, Hock Min, Slusher, Richart Elliott
• Granted Patent: US 6,986,693 B2
• Time in Patent Office: Days
• US Class Current: 313/309
• CPC Class Codes: B81B 1/00 Devices without movable or flexible elements, e.g. microcapillary devices
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: G02B 2006/12035 Materials
• CPC Class Codes: G02B 6/1225 comprising photonic band-gap structures or photonic lattices
• CPC Class Codes: H01J 1/304 Field-emissive cathodes
• CPC Class Codes: H01J 3/022 with microengineered cathode, e.g. Spindt-type
• CPC Class Codes: H01J 9/025 of field emission cathodes
• CPC Class Codes: H01L 21/0254 Nitrides
• CPC Class Codes: H01L 21/02639 Preparation of substrate for selective deposition
• CPC Class Codes: H01L 21/30612 Etching of AIIIBV compounds

Abstract

A fabrication method produces a mechanically patterned layer of group III-nitride. The method includes providing a crystalline substrate and forming a first layer of a first group III-nitride on a planar surface of the substrate. The first layer has a single polarity and also has a pattern of holes or trenches that expose a portion of the substrate. The method includes then, epitaxially growing a second layer of a second group III-nitride over the first layer and the exposed portion of substrate. The first and second group III-nitrides have different alloy compositions. The method also includes subjecting the second layer to an aqueous solution of base to mechanically pattern the second layer.

Claims

1. A method, comprising:

providing a crystalline substrate with a planar surface;

forming a first layer of a first group III-nitride on the planar surface, the first layer having a single polarity and having a pattern of holes or trenches, that expose a portion of the substrate;

then, epitaxially growing a second layer of a second group III-nitride over the first layer and the exposed portion of substrate, the first and second group III-nitrides having different alloy compositions; and

subjecting the second layer to an aqueous solution of base to mechanically pattern the second layer.

2. The method of claim 1, wherein the single polarity is group III metal-polarity.

3. The method of claim 2, wherein one of the group III-nitrides comprises aluminum and the other of the group III-nitride comprises gallium.

4. The method of claim 2, wherein the act of epitaxially growing produces one polarity of the second group III-nitride over the first group III-nitride and an opposite polarity of the second group III-nitride over the exposed portion of substrate.

5. The method of claim 2, wherein the second layer consists of first and second regions, the first region being located over the exposed portion of the substrate;

and

wherein the subjecting produces pyramids in one of the first and second regions and produces a smooth layer in the other of the first and second regions.

6. The method of claim 5, wherein the first group III-nitride is disposed between the planar surface and the second regions.

7. The method of claim 2, wherein the subjecting produces an array of columnar holes or trenches in the second layer of a second group III-nitride.

8. The method of claim 7, wherein at least some of the columnar holes or trenches uncover a portion of the planar surface of the substrate.

9. The method of claim 7, wherein the array forms a pattern with at least one discrete lattice symmetry.

10. The method of claim 1, wherein the single polarity is metal-polarity.

11. The method of claim 10, wherein the act of epitaxially growing produces one polarity of the second group III-nitride over the first group III-nitride and an opposite polarity of the second group III-nitride over the exposed portion of substrate.

12. The method of claim 10, wherein the second layer consists of first and second regions, the first region being located over the exposed portion of the substrate;

and

wherein the subjecting produces pyramids in one of the first and second regions and produces a smooth layer in the other of the first and second regions.

13. An apparatus, comprising:

a crystalline substrate with a planar surface; and

a plurality of pyramidal field-emitters located over a portion the surface;

a layer of a first group III-nitride located on another portion of the surface, the field-emitters comprising a second group III-nitride;

a layer of the second group-III nitride semiconductor being over the layer of a first group III-nitride and being free of pyramidal surface structures; and

wherein the first and second group III-nitrides have different alloy compositions.

14. The apparatus of claim 13, wherein the first group III-nitride comprises aluminum and the second group III-nitride comprises gallium.

15. The apparatus of claim 13, further comprising:

a phosphor screen located to receive electrons emitted by the pyramidal field-emitters; and

a plurality of gate electrodes located between the layer of the second group III-nitride and the phosphor screen.

16. The apparatus of claim 15, wherein the gate electrodes being mechanically supported by the layer of the second group III-nitride.

17. An apparatus, comprising:

a crystalline substrate having a planar surface;

a mechanically patterned layer of a first group III-nitride being located on the planar surface; and

a layer of a second group III-nitride being located on the mechanically patterned layer of a first group III-nitride and having a pattern of columnar holes or trenches therein; and

wherein the first and second group III-nitrides have different alloy compositions.

18. The apparatus of claim 17, wherein bottom surfaces of at least some of the holes or trenches contact the planar surface.

19. The apparatus of claim 18, wherein the layer of a second group III-nitride comprising a regular two-dimensional array of pillars.

20. The apparatus of claim 17, wherein the second group III-nitride comprises gallium and the first group III-nitride comprises aluminum.