Dynamics of charge carrier energy relaxation and recombination in undoped and P-doped GaAs quantum wells

Abstract

Character and dynamics of charge carrier energy relaxation and recombination are disclosed in detail by time delayed and time resolved cathodoluminescence experiments of undoped and doped GaAs/Ga 0.6Al 0.5As multiple quantum wells with thickness 5 nm < L z < 11 nm. At all temperatures up to room temperature the luminescence in doped and undoped samples is unambigously identified to be of excitonic origin: The luminescence decays exponentially and shows no contributions of bimolecular e-h-recombination. The excitonic recombination probability is found to increase up to one order of magnitude as compared to 3D material, it also increases strongly with decreasing temperature. p-doping induces a further increase without opening undesired impurity assisted recombination channels; Enhanced occupation of several hole subbands can increase the effect of several independent excitonic recombination channels, thus reducing the effective lifetime. Excitation intensity dependent experiments show electron and hole relaxation from higher subbands to the lower ones.