Monte Carlo calculation of high- and low-field Al_xGa_1-xN electron transport characteristics

The Monte Carlo technique is used to simulate electron transport in bulk, wurtzite phase Al_xGa_1-xN. A multi-valley analytical band model consisting of five spherical, non-parabolic conduction band valleys at the Γ, U, M, and K symmetry points of the Brillouin zone is matched to band structures of GaN and AlN. Parameters for the Al_xGa_1-xN alloy are obtained by linear interpolation. The Monte Carlo simulations are performed for ambient temperatures in the range of 300 K to 600 K. Scattering mechanisms taken into account include ionized impurity scattering and alloy scattering, in addition to deformation potential scattering (intra- and inter-valley), and polar optical phonon scattering. We present results for the electron steady-state drift velocity and the valley occupancy for electric fields up to 500 kV/cm. Low-field drift mobilities are extracted from the Monte Carlo calculations as functions of the electron concentration, of the ambient temperature, and of the alloy composition.