Photoluminescence line shape of excitons in alloy semiconductors

The study of low-temperature photoluminescence spectra of Ga₄₇{In}₅₃$As as a function of excitation intensity reveals three distinct features: With decreasing excitation intensity the excitonic line (i) narrows, (ii) shifts to lower energies, and (iii) gets increasingly asymmetric. This behavior is more pronounced in samples with a broad excitonic linewidth. At low excitation intensities linewidths of 1.2 meV for Ga₄₇{In}₅₃$As grown by chemical-beam epitaxy are found. The experimental observations are described in terms of a quantitative, semiclassical model which is based on the migration of carriers to low-energy sites of the zinc blende alloy. An expression for the photoluminescence line shape of excitons in alloy semiconductors is given for the first time. The experimental results are well described by this theoretical model.