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Photoluminescence (PL) spectroscopy is used to study the interface disorder and interface exciton transfer in single quantum wells of various well widths grown by MBE with different growth interruption times. Growth-interruption-induced microroughness on the interface terraces gives rise to peak splitting in the PL spectra with energy spacings that correspond to less than 1 ML width difference. We were able to use the well width dependence of the number of split peaks and the ratios of integrated PL intensity as an optical probe to determine the terrace areas and deduce the probability distribution of the interface roughness. Furthermore, a detailed study of the change in relative intensities of the various peaks in PL spectra taken at varying temperature reveals intra-well transfer of excitions among the localization regions and inter-well transfer. The intra-well transfer corresponds, in terms of energy, to either relaxation (by emission of an LO phonon) or thermal population (via phonon absorption).

Intrawell and interwell transfers of excitons are observed by a temperature-dependent continuous-wave photoluminescence study of growth-interrupted single quantum wells. The intrawell transfer among the interface localization areas suggests a thermodynamic equilibrium between energy relaxation via LO-phonon emission and thermal population via phonon absorption. Thermal population is dominant in wider wells while relaxation is clearly observable in a four-monolayer narrow well at low temperatures. Interwell transfer of excitons also occurs between two narrow wells. (C) 1998 Academic Press.

Growth interruption-induced microroughness is studied by photoluminescence (PL) of single quantum wells with different well widths and interruption times. Analysis of the peak splitting in the PL spectra shows that the adjacent peak splittings correspond to well width differences smaller than one monolayer. The number of split peaks increases with increasing well width, saturating when the well width exceeds 11 monolayers. This trend correlates well with the decrease in the lateral dimension of the exciton, which corresponds roughly to the minimum optically sampled area of the interface. For a given quantum well, a plot of the normalized integrated intensities of the split PL peaks versus the well width fluctuation is well described by a Gaussian distribution with an average fluctuation smaller than one monolayer. These results are consistent with the microroughness model.