Ionicity and Relaxation Anomalies at III–V Nitride Surfaces

We present first-principles study of relaxations at nonpolar surfaces of III–V nitride compounds. These surfaces show up relaxations driven by competition between dehybridization and charge transfer mechanisms. For the sake of comparison additional calculations have been performed for zincblende (110) GaAs and wurtzite (101-0) ZnO surfaces. Relaxations at (110) surfaces of zincblende AlN, GaN and InN reveal an anomalous behaviour as compared with those occurring at (110) surfaces of ordinary III–V semiconductors. On the other hand, for wurtzite (101-0) surfaces the three nitrides show up close analogies with ZnO. We trace back this behaviour to the strong ionic character of the nitrides.