Transient hot-phonon effects on the velocity overshoot of GaAs: a Monte Carlo analysis

A novel ensemble Monte Carlo algorithm has been developed to simulate nonequilibrium phonon effects in the transient and steady-state high-field conductivity of bulk n-GaAs. The interplay of the electronic intervalley transfer with the mutual drag and heating between the carriers and longitudinal optical phonons is demonstrated over a wide range of fields, temperatures and carrier densities.For the moderately high doping levels of practical interest the characteristic times for a strong phonon amplification turn out to be sufficiently long to prevent a substantial interference of phonon disturbances with the onset of valley transfer during overshoot, but modifications of up to 20 percent are found for the steady-state velocity, with a gradual change from an enhancement at low fields to a comparable decrease around the maximum and negative differential part of the velocity-field characteristics.Comparable nonequilibrium-phonon effects are found for the case of negligible (i.e. remote) ionized-impurity scattering as realized in various GaAs-based heterostructures.