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-consistent linear muffin tin orbital (LMTO) method, together with a density functional theory in local density approximation, has been employed for calculating the electronic structure of the superlattices formed from two different types of semiconductors. In particular, we report here the results for the 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 unrestrained GaAs. The calculated band offsets reveal strong sensitivity of the atomic positions in the interfacial region. The valence band offset increases (decreases) with decrease (increase) in GaN (GaAs) bond length. There appear 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 positions. 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 close 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.