Trion formation in GaAs–AlGaAs quantum dots by tunneling

Based on time-resolved microscopic photoluminescence ( μ PL ) from single self-assembled GaAs/AlxGa1−xAs quantum dots, we identify one of the emission lines as arising from positive trions (two holes and one electron) in these nominally undoped quantum dots. The trion is formed via tunneling of one electron out of the dot after optical excitation of a biexciton. The rise time of trion emission line matches the decay of the biexciton due to electron tunneling.