Bias-controlled single-electron charging of a self-assembled quantum dot in a two-dimensional-electron-gas-basedn−i-Schottky diode

Abstract

(Received 9 December 2010; revised manuscript received 12 January 2011; published 14 February 2011) We present bias-dependent micro-photoluminescence (μ-PL) spectroscopy of the neutral (X 0 ) and singly negatively-charged (X − ) excitons in single InAs/GaAs self-assembled quantum dots (QDs) embedded in the intrinsic region of an n-i-Schottky diode based on a two-dimensional electron gas (2DEG), which was obtained from a Si δ-doped GaAs layer. Using such a device structure, we demonstrate bias-controlled single-electron charging of a single QD as the QD s-shell electron state is tuned below the Fermi level. This is verified experimentally by the sequential appearance of energetically-distinct PL emission lines from the two excitons and supported by theoretical calculations. In addition, it is shown both experimentally and theoretically that simultaneous PL emission from the X 0 and X − excitons within a particular bias range is the result of a long-lived charge-nonequilibrium state due to weak tunnel-coupling between the QDs and 2DEG in our device. Further, the ability to tune the exciton transition energies via the quantum-confined Stark effect is observed, offering insight into the carrier wave function distributions in the QD and the QD material structure. Finally, we propose a number of spintronic device concepts that may be made feasible as a result of this investigation into bias-controlled carrier tunneling between a self-assembled QD and a 2DEG.