GaN surface states investigated by electrochemical studies

We present a systematic study of electrochemically active surface states on MOCVD-grown n-type GaN in aqueous electrolytes using cyclic voltammetry and impedance spectroscopy over a wide range of potentials and frequencies. In order to alter the surface states, the GaN samples are either etched or oxidized, and the influence of the surface treatment on the defect-mediated charge transfer to the electrolyte is investigated. Etching in HCl removes substoichiometric GaO, and leads to a pronounced density of electrochemically active surface states. Oxidation effectively removes these surface states.Financial support from the Deutsche Forschungsgemeinschaft (DFG STU 139=12 1), TUM.solar in the frame of the Bavarian Collaborative Research Project “Solar technologies go Hybrid” (SolTec) and the Excellence Cluster Nanosystems Initiative Munich is gratefully acknowledged.Peer Reviewe