Monte Carlo simulation of real and reciprocal space transfer of electrons in a pseudomorphically strained GaAs/In 0.15Ga 0.85As/GaAs quantum well

Abstract

We present results of transient and steady-state Monte Carlo simulations of parallel electron transport in a strained GaAs/In 0.15Ga 0.85As/GaAs quantum well structure. Both real and reciprocal space transfer is studied for electrons in the three lowest conduction bands. Confined states in the Γ, L and X valleys are described via the effective mass model, taking into account the differences in the effective masses of the well and barrier materials. Polar optical, acoustic and inter-valley phonon scattering are included for all electrons, as well as alloy scattering for those confined in the well. Emission of electrons from the well is described in terms of quantum mechanical transitions between confined and unconfined states. The average electron energy and drift velocity, as well as the real and k-space distributions, are examined for a variety of field strengths, including fields large enough that reciprocal space as well as real space transfer is probable. It was found that for low fields (≈1 kV cm −1), the steady-state is reached only after many tens of picoseconds. At higher fields (>5 kV cm −1), the structure exhibits velocity overshoot followed by a significant transient build-up of the population of the confined satellite valley states in a time of the order of a picosecond. Then, after a few picoseconds, the structure reaches the steady-state in which most of the electrons reside in unconfined states. The steady-state velocity-field characteristic for the structure exhibits a higher low field mobility than GaAs, but is very similar in general form.