Model simulation of excitons in semiconductor nanostructures at high concentration and strong disorder

Abstract

A theory of exciton formation in the presence of strong disorder is developed for a double layer semiconductor nanostructure in which electrons and holes are spatially separated. The disorder within the electron and hole layers is mainly due to structural imperfections such as interface roughness and variations in the thickness of double layer structures. We use a static lattice gas model to calculate the electron, hole and exciton densities. We consider the high carrier density case where each unit cell of the lattice gas model can have more than one electron and one hole. Our theory predicts that as the disorder increases, the relative exciton density decreases. In other words, the disorder promotes the dissociation of excitons. In addition, our theory also predicts that there must exist some critical value of the magnitude of the random potential at which the disorder changes the behavior of the exciton density.