Electronic and optical properties of III-nitrides under pressure

Results of theoretical studies of electronic and optical properties of III-V nitride compound semiconductors under pressure are presented. As representatives InN and AIN have been chosen, and for InN the pressure effects on the fundamental gap as well as the role of conduction-band filling are examined. Both the fundamental gap and the electron effective mass increase with pressure, but due to the strong non-parabolicity of the conduction band, the pressure coefficient of the mass decreases with electron concentration. Particular attention is paid to the electronic states in the gap region. The local-density gap error is avoided by performing Quasi Particle self-consistent GW calculations, which produce slightly too large gaps. Including in addition the missing electron-hole excitonic states and the gap renormalization due to electron-phonon interaction a gap reduction is obtained. The c-h correlations are deduced from solutions of the Bethe-Salpeter equation. These are further used to study excitonic states in the gap of AIN under pressure, and for the rocksalt phase a pressure induced delocalized -> localized transition is predicted. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim