THERMAL CARRIER EMISSION FROM A SEMICONDUCTOR QUANTUM-WELL

The intensity and the lifetime of quantum well (QW) photoluminescence (PL) both decrease at high temperatures. This is ascribed to thermal emission of charge carriers out of confined QW states into barrier states and subsequent nonradiative recombination processes. Corresponding activation energies reported in several publications range from the total QW binding energy Delta E(tot) of electrons and holes to half of Delta E(tot), or to the binding energy of the shallower bound particle. In pursuit of this discrepancy, we perform steady-state and time-resolved PL measurements under high- and low-excitation conditions on a series of multiple QW structures of the material systems InxGa1-xAs/GaAs, GaAs/AlxGa1-xAs, and InxGa1-xAs/InP. Covering an intensity range of more than three orders of magnitude, we find that in the high-temperature limit the final activation is associated with Delta E(tot) for both high and low excitation. We discuss our findings in the frame of a simple model for the density of states, thermalization, and recombination rates of electrons and holes.