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.

The work at the Technion was supported by the Israel Science Foundation. J.M.G. acknowledges the support of the Spanish Ministry of Science and Education.

7 páginas, 4 figuras.

Peer reviewed