Time-resolved studies of single semiconductor quantum dots

We present time-resolved optical studies of single self-assembled quantum dots. The dots were obtained by Stranski-Krastanow growth of InP on ${\mathrm{Ga}}_{0.5}{\mathrm{In}}_{0.5}\mathrm{P}.$ A selective technique based on etching after electron-beam lithography, combined with the use of an optical microscope to enhance the spatial resolution of a time-resolved photoluminescence system, enabled the observation of single quantum dots. The emission linewidth of a single InP dot is observed to be around 3 meV. The evolution of the time-resolved photoluminescence spectra was studied as a function of excitation intensity. Under intense pulsed excitation the decay is no more a simple exponential due to feeding from higher energy levels, as a result of state filling. A four-level rate equation system is successfully used to model the results.