Temperature and excitation dependence of photoluminescence line shape in InAs/GaAs quantum-dot structures

We report measurements of the temperature and intensity dependence of photoluminescence from self-organized InAs quantum dots grown by molecular-beam epitaxy on GaAs(100). At low temperatures we observed a reduction in the emission linewidth with increasing temperature that is followed by an increase in the linewidth at higher temperatures. We have also found that the photoluminescence spectra from our samples undergo an asymmetric temperature-dependent blueshift with increasing pump intensity. The dependence of the photoluminescence spectra on the temperature and degree of excitation are explained in terms of a competition between a saturable confined-electron to confined-hole transition and an excited-state transition involving the ground confined-electron state and the two-dimensional hole continuum associated with the wetting layer. At high excitation levels the photoluminescence spectra appear to be dominated by the wetting layer transition.