Removing or preventing dry etch-induced damage in Al/In/GaN films by photoelectrochemical etching
A method comprises providing a substrate comprising an n-type Al/In/GaN semiconductor material. A surface of the substrate is dry-etched to form a trench therein and cause dry-etch damage to remain on the surface. The surface of the substrate is immersed in an electrolyte solution and illuminated with above bandgap light having a wavelength that generates electron-hole pairs in the n-type Al/In/GaN semiconductor material, thereby photoelectrochemically etching the surface to remove at least a portion of the dry-etch damage.
1. A method for removing dry-etch damage from a substrate surface, the method comprising:
providing a substrate comprising an n-type Al/In/GaN semiconductor material;
dry-etching a surface of the substrate to form a dry etched surface comprising sidewalls and causing dry-etch damage to remain on the dry etched surface;
immersing the dry etched surface of the substrate in an electrolyte solution; and
illuminating the dry etched surface with above bandgap light having a wavelength that generates electron-hole pairs in the n-type Al/In/GaN semiconductor material, thereby photoelectrochemically (PEC) etching the dry etched surface to remove at least a portion of the dry-etch damage and form a PEC etched surface.
2. The method of claim 1 , wherein the sidewalls are substantially vertical.
3. The method of claim 1 , wherein the dry etched surface comprises one or more exposed planes chosen from nonpolar planes, polar planes and semipolar planes.
4. The method of claim 1 , wherein the dry etched surface comprises a semipolar plane.
5. The method of claim 1 , wherein the electrolyte solution comprises KOH at a sufficiently low molarity so as not to introduce surface roughness.
6. The method of claim 1 , wherein the PEC etching does not introduce surface roughness.
7. The method of claim 1 , wherein the PEC etching of the dry etched surface removes substantially all of the dry-etch damage.
8. The method of claim 1 , wherein the PEC etching of the dry etched surface removes all of the dry-etch damage.
9. The method of claim 1 , wherein the PEC etching of the dry etched surface reduces the dry-etch damage.
10. The method of claim 1 , wherein the PEC etching is carried out to an etch depth of more than 200 nm.
11. The method of claim 1 , wherein the PEC etching is carried out to an etch depth of about 200 nm.
12. The method of claim 1 , wherein prior to PEC etching an exposed plane of the dry etched surface has a near-band-edge (NBE) to yellow luminescence (YL) emission peak first ratio and after PEC etching the exposed plane of the PEC etched surface has a NBE to YL emission peak second ratio, the second ratio being greater than the first ratio, wherein the first ratio and the second ratio are determined using a 365 nm line of a 100 mW/cm 2 arc lamp as an excitation source.
13. The method of claim 1 , wherein the n-type Al/In/GaN semiconductor is chosen from GaN, InGaN, AlGaN, AlInGaN and combinations thereof.
14. The method of claim 1 , wherein the PEC etched surface comprises both c-plane and m-plane facets.
15. The method of claim 1 , wherein the dry etching is an inductively coupled plasma etch process or a reactive-ion etch process.
16. The method of claim 1 , wherein the sidewalls comprise a nonpolar surface.
17. The method of claim 1 , wherein the PEC etched surface comprises one or more exposed planes chosen from nonpolar planes, polar planes and semipolar planes.
18. A method for forming a p-n junction, the method comprising:
providing a substrate comprising an n-type Al/In/GaN semiconductor material;
dry-etching a surface of the substrate to form a dry etched surface therein and causing dry-etch damage to remain on the dry etched surface;
immersing the dry etched surface of the substrate in an electrolyte solution;
illuminating the dry etched surface with above bandgap light having a wavelength that generates electron-hole pairs in the n-type Al/In/GaN semiconductor material, thereby photoelectrochemically etching the dry etched surface to remove at least a portion of the dry-etch damage and form a photoelectrochemically etched surface; and
regrowing a p-type semiconductor comprising GaN on the photoelectrochemically etched surface to form a p-n junction.
19. The method of claim 18 , wherein the dry etched surface comprises one or more exposed planes chosen from nonpolar planes, polar planes and semipolar planes.
20. The method of claim 18 , wherein the PEC etching does not introduce surface roughness.
21. The method of claim 18 , wherein the PEC etching of the dry etched surface removes substantially all of the dry-etch damage.
22. The method of claim 18 , wherein the PEC etching of the dry etched surface removes all of the dry-etch damage.