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

Temperature-dependent photoluminescence measurements have been performed 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 temperature increases, while that of lower-branch polaritons narrows in the temperature range of 20-30 K. These results, which cannot be explained within the framework of the standard polariton transport model, are well reproduced by a phenomenological model that takes into account polariton scattering by bound excitons, ionized impurities, and phonons.