Optical spectroscopy of a single self-assembled quantum dot

Abstract

We apply diffraction-limited confocal optical microscopy to spatially resolve, a single self-assembled semiconductor quantum dot. We report for the first time, on the low-temperature photoluminescence spectrum of such a single dot and on its excitation intensity dependence. We demonstrate that sharp spectral lines, in the dots emission spectrum, are due to optical transitions between discrete multiexcitonic states confined within the dot. Under high excitation power, once the limited number of discrete exciton levels are fully occupied, spectrally broad emission bands are formed due to transitions which involve continuum excitonic states. In addition, we show that the single exciton recombination is almost forbidden in this InAs self-assembled quantum dot.