COUPLED ELECTRON AND NONEQUILIBRIUM OPTICAL PHONON TRANSPORT IN A GAAS QUANTUM-WELL

The self-consistent Monte Carlo technique has been used to solve coupl ed nonlinear kinetic equations for electrons and optical phonons confi ned in a GaAs quantum well. We have studied the influence of nonequili brium phonons on quasi-two-dimensional electron transport for a lattic e temperature of 30 K and for a wide range of applied electric fields. A substantial difference in generation and decay times as well as the confinement inside the GaAs/AlAs heterostructure-bounded active regio n lead to a significant growth of nonequilibrium optical-phonon popula tion generated by a heated electron gas. We have found that when the p honon generation (as well as phonon reabsorption by the quasi-two-dime nsional carriers) becomes significant, there are substantial effects-o n transport in the quantum well. We show that for low electron concent rations, the hot optical-phonon distribution reflects the main feature s of the carrier distribution; indeed, it preserves an average quasi-m omentum in the forward (opposite to electric field) direction. However , hot-phonon feedback to the electron system is found to be not essent ial in this case. For high electron concentrations, enhanced nonequili brium optical-phonon reabsorption results in phonon distribution which spreads significantly in the quasi-momentum space and essentially los es the characteristic of the forward-peaked anisotropy. The interactio ns with the confined electron subsystem typically result in an isotrop ic phonon distribution. In this case, nonequilibrium optical phonons l ead to an increase in the mean electron energy and a reduction in the carrier drift velocity. (C) 1997 American Institute of Physics.