First-principles calculation of valence band offset and the interface states in GaAs/GaN(001) superlattice

A first-principles scalar relativistic version of full-potential self-consi stent linear muffin tin orbital (LMTO) method, together with a density func tional theory in local density approximation, has been employed for calcula ting the electronic structure of the superlattices formed from two differen t types of semiconductors. In particular, we report here the results for th e lattice mismatched GaAs/GaN(001) superlattices. The calculation has been performed for the two strain modes: (i) free-standing interface, where both GaAs and GaN are strained; and (ii) GaN (strained) deposited on the unrest rained GaAs. The calculated band offsets reveal strong sensitivity of the a tomic positions in the interfacial region. The valence band offset increase s (decreases) with decrease (increase) in GaN (GaAs) bond length. There app ear a number of interface states of localized and/or resonance types which may be responsible for the sensitivity of the band offsets on the atomic po sitions. The calculated band offset ranging from 1.32 eV to 1.86 eV for the GaAs substrate and the free-standing geometries, respectively, are quite c lose to the experimental value of about 1.7-1.8 eV reported by Ding et al. (C) 1999 Elsevier Science B.V. All rights reserved.