The band structure of self-assembled InAs quantum dots, embedded in a GaAs matrix, is probed with capacitance-voltage spectroscopy and photoluminescence (PL) spectroscopy. The electron energy levels in the quantum dots with respect to the electron ground state of the wetting layer (WL) are determined from the capacitance-voltage measurements with a linear lever arm approximation. In the region where the linear lever arm approximation is not valid anymore (after the charging of the WL), the energetic distance from the electron ground state of the WL to the GaAs conduction band edge can be indirectly inferred from a numerical simulation of the conduction band under different gate voltages. In combination with PL measurements, the complete energy band diagram of the quantum dot sample is extracted.
The value of as the InAs WL was chosen to reproduce the gate voltage difference between the charging of the WL and the 2DEG in the 1D POISSON/SCHRÖDINGER simulation.
The effective distance between WL and back contact may be slightly different from the geometric value due to a spreading of charge from the back contact.