Stationary lattice mobility of holes in gallium arsenide

Abstract

The stationary lattice mobility of holes in bulk GaAs is investigated within a hydrodynamic model, including balance equations for density, current density, and energy density in each hole subband. Generalized hot displaced Maxwellians are used to calculate the input parameters of this model, which are average transport masses for each subband, velocity and energy relaxation rates for the different hole-phonon scattering channels, and transfer rates between different subbbands. The nonparabolicity of the light hole band produces a strong dependence of its transport mass on the temperature of the light hole distribution. Even for low temperatures, this transport mass is much higher than the parabolic band mass. The velocity and energy relaxation rates are extracted from the phonon scattering rates calculated in the preceeding paper. The contributions of different scattering channels to velocity relaxation depend not only on the scattering rates, but also on the average velocity of the final states after scattering. It is shown that the finite average velocities after interband scattering lead to an intrinsic coupling of the mobilities of light and heavy holes. This makes it impossible to determine the mobilities in each subband separately. Instead, the coupled mobilities are extracted from the stationary solution of the equations of motion of the hydrodynamic model. The resulting hole mobility is in good agreement with measured data up to E=40 kV cm−1 if the deformation potential d0 between holes and optical phonons is extracted from the stationary drift mobility at low field: μ0=400±40 cm2/V s and a heavy hole mass of mh*=0.50±0.02 lead to d0=27.4±5.2(μ0)±3.9(mh*) eV, where the first error is related to the measured mobility and the latter to the dependence of the calculated mobility on the heavy hole mass.