We derive expressions for electron scattering rates in mercury cadmium telluride accounting for correct wave functions in narrow-band-gap materials. These scattering rates differ slightly from the rates obtained from standard expressions for wide-band-gap materials. The difference is related to spin-flip processes and has a relatively small effect on the transport properties. However, it is very important for spin-orientation phenomena. Monte Carlo simulations have been performed to investigate the mobility and steady state velocity-field characteristics of electron transport in mercury cadmium telluride with x=0.205 at 77 K. The simulations include scattering by polar optical phonons, ionized impurities, and alloy scattering. The Pauli exclusion principle as well as the dependence of the screening length on the distribution function have been accounted for. The simulations show that the screening length increases with increasing electric field with this dependence being the strongest for low carrier concentrations. For n = 5.4 × 1015 cm−3, the inclusion of the Pauli exclusion principle and varying screening length reduces the electron velocity by 5% to 10% depending on the electric field. Velocity-field curves are in good agreement with experimental data up to the electric field where the impact ionization becomes important. We have also calculated the dependence of low-field mobility on the electron concentration, which shows reasonable agreement with experimental data.

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Monte Carlo calculation of the electron drift velocity in GaAs with a superlatticeWe have studied hole mobilities and drift velocities in undoped GaAs at 77 and 300 K using the Monte Carlo method. Two different sets of valence band parameters were used ( Vl: A = 7.98, B = 5.16, C = 6.56; V2: A = 7.65, B = 4.82, C = 7.7). The results show that the low-field mobility is sensitively dependent on the particular choice of valence band parameters. The low-field mobilities obtained were 440 cm'/V s( Yl) and 330 cm'/V s(m) at 300 K, and 17 150 cm2/V s( Vl ) and 11400 cm2/V s( V2) at 77 K. The warm hole transport coefficients /3s and y. were extracted from the drift velocity data. At 77 K, PO = -7 X 10 -9 m2/V2 and y. was estimated to be 2x 10 -lo m2/V2( Vl). At 300 K the corresponding estimated values were -2X10-13 m2/V2 and 5X lo-i4 m2/V2, respectively. The warm hole region is limited to E ~0.04 kV/cm at 77 K and to &< 10 kV/cm at 300 K. Anisotropy in the drift velocity is negligible in the warm hole region and relatively small at higher electric fields. Complete velocity saturation was not observed for the electric fields considered here (E < 60 kV/cm) .

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