Smooth Top-Down Photoelectrochemical Etching of m-Plane GaN

Abstract

Photoelectrochemical (PEC) etching of -plane GaN has been studied extensively because it is one of only a few available damage-free wet-etching techniques for this material system. Because of its nonpolar nature and low defect density, -plane GaN may benefit from PEC etching even more than -plane GaN has. With -plane GaN, it is possible to achieve smooth, controllable etching, bandgap-selective top-down etching, and deep, anisotropic etching. We have investigated PEC etching of -plane GaN in KOH and and have found etch rates ranging from less than to more than , with roughness that is crystallographic in nature but small in scale. Etch selectivity of 60:1 between and GaN is observed using PEC etching with filtered light. Anisotropic etching to depths as great as was achieved, with the sidewall profile of the etch controlled by the direction of incident light.