Homogeneous Linewidth of Type-I Localized Excitons in Type-II GaAs/AlAs Superlattices

Abstract

We investigate the homogeneous linewidth of localized type-I excitons in type-II GaAs/AlAs superlattices. These localizing centers represent the intermediate case between quasi-two-dimensional and quasi-zero-dimensional confinements. The temperature dependence of the homogeneous linewidth is gained with high precision from micro-photoluminescence spectra. We confirm the reduced exciton-acoustic-phonon interaction with decreasing dimensionality. An enhancement of the average exciton-LO-phonon interaction by localization is found in our sample. But this interaction is very sensitive to the detailed structure of the localizing centers.Introduction During the past two decades, homogeneous linewidth of excitons in several kinds of quantum well and superlattice systems has been investigated in both time [1, 2] and frequency domains [3][4][5][6][7][8][9]. Extensive information about interactions between excitons and acoustic phonons, LO phonons, free carriers and other excitons has been deduced. In these investigations, excitons are quasi-two-dimensional (Q2D). Recently, the homogeneous linewidth of quasi-zero-dimensional (Q0D) excitons confined in quantum dots, with localization energy of several hundreds of meV, has been studied by spatially resolved measurements [10,11]. In this paper, we report investigations on homogeneous linewidth of type-I localized excitons in GaAs/AlAs superlattices which have a global band alignment of type-II. The localization energies of these centers are several tens of meV. Thus, we can regard these localized excitons as intermediate in dimensionality between Q2D and Q0D excitons. The comparison with the other two kinds of excitons provides information about the influence of quantum confinement on the interactions between excitons and their environment.