UV-photoassisted etching of GaN in KOH

The etch rate of GaN under ultraviolet-assisted photoelectrochemical conditions in KOH solutions is found to be a strong function of illumination intensity, solution molarity, sample bias, and material doping level. At low e-h pair generation rates, grain boundaries are selectively etched, while at higher illumination intensities etch rates for unintentionally doped (n∼ 3×1016cm−3) GaN are ≥1000Å·min−1. The etching is diffusion-limited under our conditions with an activation energy of ∼ 0.8kCal·mol−1. The etched surfaces are rough, but retain their stoichiometry.