High field transport in GaAs/GaAlAs multiquantum wells: Theory and experiment

Abstract High field transport in GaAs/GaAlAs high mobility multiquantum wells is studied from a theoretical and experimental point of view. The quasi two dimensional properties of the multi-quantum well system are fully taken into account for both electrons and phonons. Analyzing the electronic energy loss rate due to electron-polar optical phonon coupling, it is emphasized that the electronic temperature cannot be considered as the only meaningful parameter at high fields, as it has always been the case in previous studies. For any electric field strength, the state of the electron gas is completely described by both the speed of the centre of mass and the electronic temperature. Our approach relies on the Lei-Ting model for high field transport which has been extended to include more than one subband and the LO phonon eigenmodes in GaAs/GaAlAs heterostructures. Two multi-quantum wells have been experimentally studied: the speed of the centre of mass and the electronic temperature are experimentally determined in steady state conditions. A good agreement between theory and experiment is found for the energy loss rates assuming a finite phonon lifetime of 5 ps but the model underestimates the high field drift velocities in this hypothesis.