Crystallographic wet chemical etching of III-nitride material

• US 6,294,475 B1
• Filed: 06/23/1999
• Issued: 09/25/2001
• Est. Priority Date: 06/23/1998
• Status: Expired due to Term

• Current Assignee: Boston University, Trustees of Boston University
• Original Assignee: Trustees of Boston University
• Inventors: Schubert, E. Fred, Stocker, Dean A.
• Primary Examiner(s): KUNEMUND, ROBERT M
• Application Number:
  US09/338,709
• Time in Patent Office: 825 Days
• Field of Search: 438/712, 438/718, 438/749
• US Class Current: 438/712
• CPC Class Codes: H01L 21/30617 Anisotropic liquid etching

Abstract

A method of processing III-Nitride epitaxial layer system on a substrate. The process includes exposing non-c-plane surfaces of the III-nitride epitaxial layer system, for example by etching to a selected depth or cleaving, and crystallographical etching the epitaxial layer system in order to obtain crystallographic plane surfaces. In an exemplary embodiment, the III-Nitride epitaxial layer system includes GaN. In accordance with one aspect of the exemplary embodiment, the etching step includes reactive ion etching in a chlorine-based plasma, PEC etching in a KOH solution or cleaving, and the crystallographical etching step includes immersing the epitaxial layer system in a crystallographic etching chemical, such as phosphoric acid, molten KOH, KOH dissolved in ethylene glycol, sodium hydroxide dissolved in ethylene glycol, tetraethyl ammonium hydroxide, or tetramethyl ammonium hydroxide. Speaific etching planes are chosen in accordance with varying the orientation of the exposing step, the etching chemical, and the temperature at which the epitaxial layer system is etched.

Claims

1. A method of processing a III-Nitride epitaxial layer system provided on a substrate, comprising:

exposing non-c-plane surfaces of said III-Nitride epitaxial layer system; and

crystallographically etching said epitaxial layer system in order to obtain crystallographic plane surfaces.

2. The method of claim 1, wherein said III-Nitride epitaxial layer system comprises GaN.

3. The method of claim 1, wherein said exposing step comprises reactive ion etching in a chlorine-based plasma, PEC etching in a KOH solution or cleaving.

4. The method of claim 1, wherein said crystallographically etching step comprises immersing said epitaxial layer system in a crystallographic etching chemical.

5. The method of claim 4, wherein said chemical comprises phosphoric acid, molten KOH, KOH dissolved in ethylene glycol, sodium hydroxide dissolved in ethylene glycol, tetraethyl ammonium hydroxide or tetramethyl ammonium hydroxide.

6. The method of claim 4, wherein specific etching planes are chosen in accordance with varying the orientation of said first etching step, said etching chemical, and the temperature at which said epitaxial layer system is etched.

7. The method of claim 1, wherein a laser diode is processed.

8. The method of claim 1, wherein a bipolar transistor is processed.

9. A method of processing a III-Nitride epitaxial layer system provided on a substrate to produce a laser diode, comprising:

reactive etching said III-Nitride epitaxial layer system to a selected depth; and

crystailographically etching said epitaxial layer system in order to obtain substantially atomically smooth vertical surfaces.

10. A method of processing a III-Nitride epitaxial layer system provided on a substrate to produce a bipolar transistor, comprising:

photoenhanced wet etching said III-Nitride epitaxial layer system to a selected depth; and

crystallographically etching said epitaxial layer system in order to obtain undercut walls and substantially atomically smooth surfaces.

11. A method of processing a III-Nitride epitaxial layer system comprising:

providing a III-Nitride epitaxial layer system on a substrate; and

wet chemical crystallographic etching said epitaxial layer system along non-c-plane crystal directions.

12. The method of claim 11, wherein said epitaxial layer system comprises GaN.

13. A method of processing a III-Nitride epitaxial layer system comprising:

providing a III-Nitride epitaxial layer system on a substrate; and

crystallographically etching said epitaxial layer system by immersing said epitaxial layer system into a liquid chemical.

14. The method of claim 13, wherein said epitaxial layer system comprises GaN.

15. The method of claim 13, wherein said liquid chemical includes molten KOH, KOH dissolved in ethylene glycol, NaOH dissolved in ethylene glycol, phosphoric acid, tetraethyl ammonium hydroxide, or tetramethyl ammonium hydroxide.

16. The method of claim 13, wherein said liquid chemical is heated.

17. A method of processing a III-Nitride epitaxal material system comprising:

providing a III-Nitride epitaxial layer system on a substrate;

etching said epitaxial layer system along c-plane crystal directions; and

wet chemical crystallographic etching said epitaxial layer system along non-c-plane crystal directions.

18. The method of claim 17, wherein said epitaxial layer system comprises GaN.

19. The method of claim 17, wherein said first etching step comprises reactive ion etching, ion milling, low-energy electron enhanced etching, photo-electrochemical etching, chemically assisted ion beam etching, or enhanced forms of reactive ion etching.

20. A method of processing a GaN layer in order to produce semiconductor laser facets comprising:

providing a GaN on a substrate; and

wet chemical crystallographic etching said GaN layer in order to obtain substantially atomically flat surfaces.