Valence band offsets and interface states of polar GaN/SiC (001) 2 x 2 superlattices

We present the results of a first principles scalar relativistic version of full potential self-consistent linear muffin tin orbital method with a den sity functional theory in the local density approximation for the structura l and electronic properties of the polar GaN/SiC (001) superlattices. The c alculation has been performed for two types of the reconstructed c (2 x 2) interfaces containing two types of atoms (i) Si (50%) and Ga (50%) and (ii) C (50%) and N (50%) after using a relatively large supercell of 16 layers. The relaxation of atoms in the various layers has been considered. The cal culated band offsets reveal strong sensitivity on the atomic positions in t he interfacial region and quantitative estimates for changes in the valence band offsets (VBO) with changes in the interfacial interatomic bond length s have been predicted. The interface states have been obtained for the rela xed surfaces. The calculated values of VBO (averaged) are 1.01 eV for (Si-G a) mixed interface and 0.29 eV for the (C-N) mixed interface in the minimum energy configurations. The present values of VBOs are on the lower energy side as compared to a pseudopotential calculation by Stadele et al. and may be considered more reliable as has been discussed later in the present art icle. Our calculated values of the valence band offsets for the mixed [Si,G a] interface are quite near to the estimated experimental value. (C) 2001 E lsevier Science B.V. All rights reserved.