Hot Electrons in the Tunnel-Coupled Quantum Wells under Intersubband Excitation

Abstract

Nonequilibrium electron distribution in the tunnel-coupled double quantum wells (DQWs) may be achieved both under usual excitation methods (passing of current or interband photoexcitation), and due to intersubband transitions. The latter case is realized in recent experiments,1,2 where both infrared and submillimeter (SM) pumping were used. Under resonance intersubband excitation, except of nonlinearity mechanism caused by the change of the electron temperature T e , an additional mechanism caused by the redistribution of electrons between these states is important. Such a redistribution causes change of the transverse self-consistent electric field which changes the intersubband energy and, consequently, abruptly increases or decreases (depending on DQWs parameters and excitation frequency) the efficiency of pumping. In this paper we consider conditions for the transformation between linear and nonlinear excitation regimes, and also for saturation with increase of the pumping intensity. Moreover, the conditions for realization of the bistability in DQWs under resonance SM pumping are considered. The self-consistent (Hartree approximation) description of the energy states in DQWs and balance equation for concentration are used for calculation of rectification voltage (i.e. transverse voltage induced by the pumping) and nonlinear absorption. These results are compared with experimental data for SM excitation.2