Time Resolved Spectroscopy of GaAs/AlGaAs Quantum Well Structures

Abstract

Optical spectroscopic techniques like absorption, photoluminescence, and photoluminescence excitation spectroscopy are widely used to characterize and investigate the properties of quantum wells (QW) and provide significant information on the electronic structure of the respective samples. Conclusions on the dynamics of nonequilibrium carriers, however, generally cannot be drawn from stationary experiments but require time resolved spectroscopy techniques. The dependence of the fundamental relaxation and recombination processes on the dimensionality, i.e. the thickness L_Z and L_b of the quantum well and barrier layers, respectively, is one of the key questions as far as QW are considered. In addition, new relaxation processes come into play in QW, which are not present in bulk material, like carrier trapping from the barriers into the QW, intersubband scattering between states with different quantum number, and intervalley scattering including spatially seperated bands (real space transfer).