Optical evidence of the direct-to-indirect-gap transition in GaAs-AlAs short-period superlattices

Luminescence dynamics in type-II GaAs/AlAs superlattices near the type-I to type-II crossover

“…The transformation of short-period GaAs/AlAs superlattices from type-I to type-II has attracted much research since it was demonstrated by Danan et al 1 This is due to the different properties of the two types of transitions in their densities of states, radiative decay times, and inhomogeneous broadenings. Subpicosecond scattering of the ⌫ electrons in GaAs to the X point in the adjacent AlAs layers makes these structures suitable as saturable absorbers.…”

Emission from Mesoscopic-Size Islands Formed in a GaAs/AlAs Double Layer Structure

“…Such a spectrum is characteristic of type-II GaAs/AlAs systems for which the lowest electronic state in the AlAs well is of X XY symmetry and the X Z state is located a few meV higher. The observed ordering of X XY and X Z states is a subtle result of the interplay between the confinement and strain [5,6]. The spectra change considerably under higher excitation intensities.…”

Physics of GaAs/AlAs Superlattices

“…2, where we have defined the SPS period: Ρ = LGaAs+LAlAs, and the mean Al concentration: Al = LAlAs /P. Typically, for the value Qc = 0.67 that we have determined [13], we get "indirect" type II SPS when LGaAs <4 nm and xΑl > 0.35 (these values depend slightly on the bulk material parameters used, and thus on temperature). As we shall see below, these EFA predictions are surprisingly well confirmed by photoluminescence and other spectroscopic experiments made up to now.But it is still possible, and helpful, to go further into the details of the X-state symmetry, within this framework.…”