Electron transport through a single InAs quantum dot

InAs islands were embedded in the channel of an n-doped GaAs/AlGaAs high electron mobility transistor structure and a $60\times 100{\mathrm{nm}}^2$ constriction was defined by lithography based on the atomic-force microscope and subsequent wet chemical etching. Compared to an unpatterned device a strong shift of the threshold voltage to higher gate voltages and well-defined peaks were observed at the onset of the conductance. The energetic position as well as the magnetic-field-induced shift of the peaks confirm that electron transport through the p shell of a single InAs quantum dot (QD) is observed. Our experimental data are in excellent agreement with calculations based on a simple parabolic quantum dot potential. A Coulomb blockade energy of ≈12 meV is determined for electrons in the first excited QD state.