Calculation of the wave-vector-dependent interband impact-ionization transition rate in wurtzite and zinc-blende phases of bulk GaN

We present calculations of the wave-vector-dependent interband impact-ionization transition rate in wurtzite and zinc-blende phases of bulk GaN. The transition rate is determined by integrating Fermi's golden rule for a two-body, screened Coulomb interaction over the possible final states using a numerically generated dielectric function and pseudowavefunctions. The full details of all relevant conduction and valence bands in zinc-blende and wurtzite GaN are included from an empirical pseudopotential calculation. It is found that the transition rate is consistent with a relatively "soft" threshold energy.