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 whic h we assign to single-electron tunnelling through self-assembled InAs quant um dots between two three-dimensional electrodes. From the magnetic field d ependence of the onset of the current steps, we determine the lateral exten sion 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 attribut ed to tunnelling through charged dots. A similar structural dot size is mea sured independently by transmission electron microscopy on the same wafer a nd by atomic force microscopy on control samples with InAs dots on a GaAs o r an AlAs surface, respectively.