Exciton-polariton light absorption in bulk GaAs and semiconductor superlattices

Abstract

A comparative study of the temperature dependence of the absorption edge has been performed with thin single-crystal wafers of bulk GaAs and multilayer quantum-size GaAs/Ga0.3Al0.7As structures with the well and barrier thicknesses La=Lb approximately=135 Å in the temperature range T=4-300 K. The total number of periods was N>20. The authors consider the quantity K*, which is proportional to the integral absorption coefficient calculated as a product of the line halfwidth and the optical density at the exciton band maximum. In bulk samples K* shows a sharp increase by nearly an order of magnitude, up to T* approximately= 110 K, and then remains roughly constant. The temperature T* may be considered as critical for the excitonic polariton-mechanical exciton transition. A similar behaviour of K* was observed for superlattices with a slightly increasing integral absorption up to a temperature of T* approximately=20 K. This fact is considered as evidence for the polariton nature of light absorption at T