Photoluminescence spectroscopy in GaAs/AlAs superlattices as a function of temperature and pressure: The influence of sample quality

Abstract

Photoluminescence experiments are reported on GaAs/AlAs short-period superlattices as a function of temperature (1.5–80 K) and hydrostatic pressure (0–80 kbar). Molecular-beam-epitaxial growth at 650 °C was found to be superior to that at lower temperatures (620 °C and 590 mDC) and allowed the effects of sample perfection on photoluminescence phenomena to be studied. Superlattices with (12,8), (11,8), (11,10), and (10,8) GaAs/AlAs monolayers were studied, near the type-I–type-II transition. The reduction in photoluminescence intensity with temperature was found to be much less rapid for superlattices grown at 650 °C, indicative of a lower defect density at the higher growth temperature. These results are consistent with an analysis of the variation of recombination lifetime [τ(P)] with pressure. It is deduced that nonquadratic behavior in τ(P) is at least partly due to extrinsic, nonradiative transitions, which are sample dependent and are less significant at the higher growth temperature. The data suggest that results of a recent calculation of the absolute recombination times for the (12,8) sample must be applied with caution.