ZINCBLENDE GAN - AB-INITIO CALCULATIONS

The purpose of this paper is to contribute, on a theoretical basis, an understanding of future wide-gap device concepts and applications bas ed on III-V nitride semiconductors. The electronic properties of zinc- blende structure GaN and their (110), (100) and (111) surfaces are inv estigated using ab initio calculations based on the full potential lin ear augmented plane-wave (FPLAPW) method within the large unit cell ap proach, and on the molecular Gaussian-92 code. Lattice constant, cohes ive energy, bulk modulus are obtained from total energy calculations. Light-hole and heavy-hole effective masses along (100), (111) and (110 ) directions and electron masses at Gamma point are extracted from ban d structure calculations and compared with previous ones based on pseu dopotential methods. The hydrostatic pressure dependence of the Gamma Gamma, Gamma X and Gamma L energy gaps are also obtained. Comparing ou r band structure and 'molecular cluster' calculations, the relaxations of the surfaces are found to be mostly determined by local rehybridiz ation or valence effects and are basically independent of energy band features. (C) 1997 Elsevier Science S.A.