Sequential Photon Emissions from Quad-excitons in Single GaAs Quantum Dots

Abstract

We studied photoluminescence (PL) spectra of a single self-assembled GaAs quantum dot (QD) grown by modified droplet epitaxy. The single QD exhibits several sharp peaks in the PL spectrum indicating the formation of multi-excitonic complexes. Most of these peaks are originated from the recombinations of electron-hole pairs in the lowest level of the QD. We observed several emission peaks arising from recombinations from the second level of the QD at the condition of strong excitation. The difference of the recombination energy between the lowest and second levels is about 30 meV. We identified the emissions of tri-excitons and quad-excitons in the PL spectrum by single photon correlation spectroscopy. Quad-exciton, which is the four-exciton complex, emits correlated four photons in the cascade recombination. We observed bunching of photons emitted from the cascade by cross-correlation measurements.