HOT-ELECTRON ENERGY AND MOMENTUM RELAXATION IN GAAS/ALAS AND GAAS/GA1-XALXAS MULTIPLE-QUANTUM WELLS

Experimental results on high electric field longitudinal transport in GaAs/AlAs and GaAs/Ga1-xAlxAs multiple quantum wells (MQW) are presented and compared with the prediction of a dielectric continuum model. We draw from our experiments the following four conclusions. (i) In GaAs/Ga1-xAlxAs systems the dominant energy and momentum relaxation mechanism is through scattering with GaAs-modes. (ii) However, in GaAs/AlAs systems the AlAs interface mode is dominant in relaxing the energy and momentum of the quantum well electrons. (iii) The hot electron momentum relaxation as obtained from the high-field drift velocity experiments is strongly affected by the production of hot phonons as expected from a model involving a non-drifting hot phonon distribution. (iv) The importance of the AlAs interface mode in GaAs/Ga1-xAlxAs MQW is not the result of the intrinsic scattering rate but related to its shorter lifetime, compared to GaAs modes.