Electron capture dynamics into self-assembled quantum dots far from equilibrium with their environment

We report studies of the electron capture process in self-assembled quantum dots (SAQDs) far from equilibrium with their environment and at large distance to the reservoirs. Deep level transient spectroscopy is used to determine the capacitance transients in response to bias voltage pulses, from which the capture rates are obtained as a function of the temperature and the quantum dot occupancy. The observed activated character of the capture suggests that the dominant electron source is the back contact. A model is developed based on electrons diffusing from the reservoir across the flat band region and getting captured in the SAQDs after overcoming the barrier formed by the space charge region between its onset and the quantum dots. For small barriers, we identify a distinct tunneling contribution to the capture current.