We identify fundamental mechanisms of electron escape from self-organized InAs quantum dots (QD’s) in a vertical electric field by time-resolved capacitance spectroscopy. Direct tunneling and a thermally activated escape process are observed. The QD electron ground and first-excited states are concluded to be located ∼190 and ∼96 meV below the GaAs matrix conduction band, respectively. Our experimental results and their interpretation are in good agreement with eight-band $\mathbf{k}\cdot \mathbf{p}$ calculations and demonstrate the importance of tunnel processes.

• Received 29 April 1999

DOI:https://doi.org/10.1103/PhysRevB.60.14265