Microfabrication of GaN groove on sapphire substrate treated selectively by electron‐beam

Abstract

H 2 -cleaned sapphire substrate was treated with an electron-beam aiming at polarity-selective growth of GaN film by using metalorganic chemical vapor deposition (MOCVD). It was found that GaN growth on the sapphire substrate treated with an electron-beam was suppressed like GaN growth on a SiO 2 mask. GaN grooves having the fluctuated sidewalls were fabricated as designed by lithography patterns due to the selective growth. The groove sidewalls became smoother after etching by dipping in a KOH aqueous solution. This improvement was enhanced for the grooves oriented along <11 2 0> direction, compared to those along <1 1 00> direction.

Selective growth of GaN on sapphire substrates treated with focused femtosecond laser pulses

“…To solve these problems, we have previously investigated substrate treatment procedures; the sapphire substrate surface was treated and patterned with an electron beam prior to MOCVD growth of GaN [17]. Over the surface areas exposed to electron beam, GaN hardly grows, resulting in groove-like structures with dimensions ranging from micrometer to submicrometers.…”

Lateral Polarity Control in GaN Based on Selective Growth Procedure Using Carbon Mask Layers

“…Specifically, for patterning process, we employed carbon mask layers to avoid the etching process. 11,12) We have found that this carbon mask layer can be formed onto a sapphire substrate via modification of an organic polymer layer with focused laser irradiation, 11) as well as electron beam exposure. 12) After performing selective growth, this carbon mask layer was removed by thermal treatments, and the re-exposed sapphire surface was nitrided, so that the polarity of GaN was locally inverted during MOCVD growth.…”