Size determination of InAs quantum dots using magneto-tunnelling experiments

Tunnelling experiments through GaAs-AlAs-GaAs structures with InAs embedded in the AlAs barrier show steps in the current-voltage characteristics which we assign to single-electron tunnelling through self-assembled InAs quantum dots between two three-dimensional electrodes. From the magnetic field dependence of the onset of the current steps, we determine the lateral extension of the electronic wave function in the dot to 4 nm, corresponding to a dot of 14 nm in diameter. Replica of steps at higher voltages are attributed to tunnelling through charged dots. A similar structural dot size is measured independently by transmission electron microscopy on the same wafer and by atomic force microscopy on control samples with InAs dots on a GaAs or an AlAs surface, respectively.