Talk abstract

The effective masses are fundamental quantities of semiconductors, used in various experimental and theoretical investigations. We present calculations of the electronic structure near the band edges in intrinsic and heavily n-type doped GaN and AlN, for both the wurtzite and the zinc-blende polytypes. The electronic structures of the intrinsic materials were obtained from a full-potential linearized augmented plane wave (FPLAPW) method within the generalized gradient approximation (GGA). 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 the 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 Fr�hlich Hamiltonian for large polarons, resulting in the effective polaron masses. The effects on the masses due to doping were investigated by using a zero-temperature Green's function formalism within the random phase approximation (RPA).