Theoretical study of electron initiated impact ionization rate in bulk GaN using a wave vector dependent numerical transition rate formulation

In this paper, we present ensemble Monte Carlo based calculations of electron initiated impact ionization in bulk zincblende GaN using a wavevector dependent formulation of the interband impact ionization transition rate. These are the first reported estimates, either theoretical or experimental, of the impact ionization rates in GaN. The transition rate is determined from Fermi's golden rule for a two-body screened Coulomb interaction using a numerically determined dielectric function as well as by numerically integrating over all of the possible final states. The Monte Carlo simulator includes the full details of the first four conduction bands derived from an empirical pseudopotential calculation as well as all of the relevant phonon scattering mechanisms. It is found that the ionization rate has a relatively 'soft' threshold.