HOT-ELECTRON TRANSPORT IN GAAS QUANTUM-WELLS - EFFECT OF NONDRIFTING HOT PHONONS AND INTERFACE ROUGHNESS

The influence of a non-equilibrium population of LO phonons (hot phono ns) on hot-electron energy and momentum relaxation in modulation-doped GaAs quantum wells are studied both experimentally and theoretically. The experimental results on high-field parallel transport indicate st rongly that: (i) non-equilibrium phonons in GaAs quantum wells, contra ry to the assumptions made in the conventional theories, are non-drift ing; (ii) therefore, the production of hot phonons not only reduces th e energy relaxation rate but also enhances the momentum relaxation rat e; (iii) the enhancement of the momentum relaxation at high fields inh ibits negative differential conductivity via real space transfer or in tervalley transfer; (iv) the enhancement of the momentum relaxation ra te also reduces the drift velocity at high fields, which is detrimenta l to the speed of the hot electron devices; (v) hot phonon effects inc rease with increasing 3D carrier concentration. The results are compar ed with a comprehensive theoretical model involving non-drifting hot p honons and scattering from remote impurities and interface roughness. The agreement between the theory and the experiments is excellent.