Theory of photoluminescence line shape due to interfacial quality in quantum well structures

We have developed a simple theory to understand the role of interfacial quality in the line shape of photoluminescence spectra in quantum wells. The interface is described in terms of microscopic fluctuations δ1 and δ2, where δ1 is the local fluctuation in the well width and δ2 is the lateral correlated extent of the fluctuation. We make use of Lifshitz theory of disordered alloys to determine the probability of distribution of fluctuations in the well size over the extent of the optical probe, i.e., the exciton. The line shape is then calculated from this probability distribution. Both δ1 and δ2 are found to be important in controlling the linewidths in quantum wells. The use of this quantitative theory to characterize the microscopic nature of interfaces is discussed.