Electron energy structure of self-assembled In(Ga)As nanostructures probed by capacitance-voltage spectroscopy and one-dimensional numerical simulation

Abstract

The electron energy structure of self-assembled In(Ga)As/GaAs nanostructures, quantum dots, and quantum rings was studied with capacitance-voltage spectroscopy and one-dimensional numerical simulation using Poisson/Schro¨dinger equations. The electron energy levels in the quantum dots and quantum rings with respect to the electron ground state of the wetting layer were determined directly from capacitance-voltage measurements with a linear lever arm approximation. In the regime where the linear lever arm approximation was not valid anymore (after the charging of the wetting layer), the energy difference between the electron ground state of the wetting layer and the GaAs conduction band edge was obtained indirectly from a numerical simulation of the conduction band under different gate voltages, which led to the erection of complete electron energy levels of the nanostructures in the conduction band.