Deconvolution of the light- and heavy-hole free exciton fine structure in AlxGa1−xAs---GaAs multi quantum wells using photoluminescence excitation spectroscopy

Sharp-line structure associated with both the light-hole free exciton (LHFE) and heavy-hole free exciton (HHFE) transitions has been observed in multi-quantum-well (MQW) structures of four well sizes in photoluminescence (PL) and reflection spectra. These spectra have been deconvulated using photoluminescence excitation spectroscopy (PLE). The LHFE and HHFE sharp-line structure is associated with interface structure composed of growth islands at the interface between the barriers and the wells. Estimates of the average interface island sizes for the four different MQW structures are made based on theoretical modelling. A correlation is established between particular LHFE fine structure components and specific HHFE fine structure components. A model is developed to account for the LHFE and HHFE fine structure based on a non-random distribution of the interface structure. The physical location of the excitons is demonstrated to be in regions of the wells with essentially identical interfacial microstructure. Evidence for diffusion of excitons from effectively narrow well regions to wider well regions is presented.