Photoluminescence and photoluminescence excitation studies on GaAs/AlAs short period superlattices near the direct/indirect crossover

Abstract

A photoluminescence (PL) and PL excitation (PLE) investigation of GaAs/AlAs superlattices near the direct to indirect gap, type I to type II superlattice crossover is reported. The nature of the phonon coupling, the magnitude of the Stokes’ shifts between PL and PLE, and the dependence of the PL spectra on hydrostatic pressure are studied. From these results a change of the GaAs width (d) by just 1 monolayer (ML) from 12 to 11 ML is shown to cover the range from near coincidence of the GaAs (Γ) and AlAs (X) conduction band minima, but with type I, direct gap character dominant at d=12 ML, to clearly indirect gap, type II behavior at d=11 ML.