Self-assembled quantum dots as probes for Landau-level spectroscopy

We report on capacitance–voltage measurements of an inverted two-dimensional electron gas (2DEG) with a layer of self-assembled InAs quantum dots in its immediate vicinity. A variable frequency approach enables us to determine the position of the Quantum dots-induced charging peaks for the first six electrons per dot in magnetic fields up to View the MathML source. Using the first s-electron as an energetic reference we monitor the oscillations of the 2DEG Fermi energy as a function of the applied magnetic field. Because in the present experiment, also the energy scale of the oscillations can be determined a detailed comparison with theoretical models becomes possible. We find good agreement at low and intermediate fields, when a Gaussian density of states with a constant background is assumed. The discrepancy found for highest fields investigated suggests that more sophisticated models are necessary in this regime.