Spectroscopy of a single semiconductor quantum dot at negative and positive discrete charge states
We study optically single self-assembled quantum dots embedded within the wide quantum well of a mixed type quantum structure. We compare the steady state and pulsed photoluminescence spectra of these dots to those of previously studied "regular" dots. We unambiguously identify experimentally emission from various discrete charge state of the dots. We provide means for optically tune the charge state of the dot, both negatively and positively. Our observations are used to accurately determine the asymmetry between the quantum dots' confined electron and hole envelope wavefunctions.