Assessing the electronic states of InAsP/GaAs self-assembled quantum dots by photolumincescence and modulation spectroscopy

In this work we study, using photoluminescence (PL) and photomodulated transmission experiments (PT) we investigate the eletronic states of InAsP/GaAs QDs as a function of excitation power. PL measurements were performed from 15~K to 290~K, with the excitation power varying from 2 to 30~$W/cm^{2}$. We were able to identify the recombination from the QDs ground state from PL experiments and the contribution of the InAsP wetting layer (WL) from PT experiments which has never been observed for these QDs. Specifically, for the InP material, WL recombination is so close in energy to the QD transition that it is possible that both are seen simultaneously as a single PL band. Also, for the InAsP samples with higher As contents excited QD states were identified, since the confining potential is deeper in this situation. The WL presents an isotropic behavior, as expected. Modulated transmission shows spectral structures with different ranges of line widths, which are consistent with the QD and WL assignments given after the PL analysis.