The etch rate of GaN under ultraviolet-assisted photoelectrochemical condit
ions in KOH solutions is found to be a strong function of illumination inte
nsity, 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 sim
ilar to 3 x 10(16) cm(-3)) GaN are greater than or equal to 1000 Angstrom.m
in(-1). The etching is diffusion-limited under our conditions with an activ
ation energy of similar to 0.8kCal.mol(-1). The etched surfaces are rough,
but retain their stoichiometry.