TEMPERATURE-DEPENDENCE OF THE FREE-EXCITON-EMISSION LINEWIDTH IN HIGH-PURITY INP

Temperature-dependent photoluminescence measurements have been perform ed to study the linewidth of the n=1 free-exciton transition in a high -purity n-type InP epilayer. The spectra reveal that the linewidth of the emission from upper-branch polaritons broadens rapidly when the te mperature increases, while that of lower-branch polaritons narrows in the temperature range of 20-30 K. These results, which cannot be expla ined within the framework of the standard polariton transport model, a re well reproduced by a phenomenological model that takes into account polariton scattering by bound excitons, ionized impurities, and phono ns.