Disorder-induced localization in superlattices

Abstract

Abstract Purposely disordered GaAs/AlxGa1−x As short period superlattices, followed by an enlarged well, were grown by molecular beam epitaxy. Selective excitation photoluminescence and photoluminescence excitation measurements were performed to study the energy dependence of the motion of resonantly photocreated excitons in disordered superlattices. The disorder was introduced as a random succession of different well widths distributed according to a Gaussian function. We report the existence of different energy regions in the superlattice bands, corresponding to extended and spatially confined (localized) states. A calculation of the superlattice miniband spectrum suggests that the coupling between similar wells although on different spatial region atlows excitonic diffusion for some energies. We compare different samples with different disorder distribution. The role of the enlarged well in driving the vertical diffusion is discussed.