Carrier kinetics in quantum dots through continuous wave photoluminescence modeling: A systematic study on a sample with surface dot density gradient

A systematic study is presented of continuous wave (cw) photoluminescence (PL) of self-assembled quantum dots (QDs) grown on GaAs (001) by molecular-beam epitaxy as a function of excitation intensity and QD density. The sample used in this work was grown under nonisotropic indium flux that resulted in a QD density gradient across the sample surface ranging from 0 to 1.8 x 10(11) cm(-2). The carrier kinetics in the sample is described by a set of coupled rate equations through which the cw PL data from the GaAs barrier, wetting layer (WL), and QDs were simulated as a function of the excitation intensity and QD density. By comparing the PL data with our simulations we infer that carrier capture into the QD occurs directly from GaAs barrier. Auger and phonon-assisted carrier capture from the WL were found to give negligible contribution. With an increase of the QD density we observe an increase of the nonradiative recombination rates of the barrier and at the WL, which we tentatively correlate with the increase of surface and interface recombination rates. Furthermore, we noticed that the variation of the coefficients used in our model in order to simulate the experimental results over the entire QD density range studied is strongly correlated with the changes in sample morphology. In particular, the behavior of the capture rate as a function of the QD density allowed us to determine a QD capture cross section from the GaAs barrier equal to 1.5 x 10(-11) cm(2). (C) 2003 American Institute of Physics.