Effects of photoelectrochemical etching of n-polar and Ga-polar gallium nitride on sapphire substrates

We studied the effects of photo electrochemical (PEC) etching by using various concentrations (1, 2, and 4 M) of KOH solutions on both Ga- and N-face GaN layers on sapphire substrates. The Ga-face was chemically stable for KOH solutions, while by sharp contrast the KOH could etch the N-face, where the 6-fold symmetry was observed after the PEC etching. Surface texturing of GaN-based light emitting diodes and solar cells by KOH-based PEC etch could enhance the efficiency of GaN-based photonic devices by increasing the number of the scattering events and randomly changing the angles of the light.