Electron transport through a single InAs quantum dot

InAs islands were embedded in the channel of an n-doped GaAs/AlGaAs high el ectron mobility transistor structure and a 60 x 100 nm(2) constriction was defined by lithography based on the atomic-forte microscope and subsequent wet chemical etching. Compared to an unpatterned device a strong shift of t he threshold voltage to higher gate voltages and well-defined peaks were ob served at the onset of the conductance. The energetic position as well as t he magnetic-field-induced shift of the peaks confirm that electron transpor t through the p shell of a single InAs quantum dot (QD) is observed. Our ex perimental data are in excellent agreement with calculations based on a sim ple parabolic quantum dot potential. A Coulomb blockade energy of approxima te to 12 meV is determined for electrons in the first excited QD state.