Effective electron and hole masses in intrinsic and heavily n-type doped GaN and AlN

Abstract

We have investigated the electronic structure near the band edges in intrinsic and heavily n-type doped GaN and AlN. Both the wurtzite and the zinc-blende polytypes have been considered. The electronic structures of the intrinsic materials were obtained from a full-potential linearized augmented plane wave calculation. We show the importance of performing a fully relativistic calculation. For instance, the hole mass in cubic AlN is a very large and negative quantity if spin-orbit coupling is excluded, whereas the fully relativistic calculation gives a relatively small and positive value. The electron-phonon coupling was taken into account according to the Fröhlich Hamiltonian for large polarons, resulting in effective polaron masses. The effects on the effective electron masses due to doping were investigated by using a Green's function formalism within the random phase approximation and with a local-field correction according to Hubbard.