Kinetics of accumulation of excess holes under photoexcitation and their relaxation in GaAs/AlGaAs shallow quantum wells

The kinetics of accumulation of long-lived excess holes that appear in GaAs/Al$_{0.05}$Ga$_{0.95}$As shallow quantum wells under above-barrier photoexcitation and their relaxation is studied by time-resolved photoluminescence spectroscopy. The establishment of a steady state in the nonequilibrium electron-hole system under various combinations of above-barrier and intrawell excitation is also investigated. It is found that the temperature dependence of the excess-hole relaxation time (their lifetime in the quantum wells) exhibits activation behavior with two activation energies. It is established that excitons produced by nonresonant intrawell excitation undergo efficient cooling as they scatter off accumulated long-lived holes.