Hot carrier relaxation processes and nonequilibrium phonon effect in multiple quantum well structures

Abstract

We have used a picosecond nonlinear optical correlation technique to investigate the relaxation processes of hot nonequilibrium carriers in multiple quantum well structures. The average energy loss time constant π_avg of the hot electrons was measured. By solving the average energy loss rate equation of carriers and the hot phonon rate equation, taking both the phonon emission and reabsorption into account, we show that π_avg is the sum of the electron-phonon interaction time constant and the nonequilibrium phonon decay time, assuming only a single mode of phonons are involved. It is found that the temperature will be higher and/or the energy loss rate of the electron system will be slower as the quantum well width decreases, or the excitation density increases, or the degree of the lattice mismatch between the well layer and the barrier layer increases in the case of strained quantum wells.