Modeling and experimental results for C(V) in an abrupt isotype n Al0.5Ga0.5As/GaAs heterojunction

The differential capacitance C of an abrupt isotype n Al_0.5 Ga_0.5As/GaAs heterojunction has been modeled by directly calculating the dependence of the space charge on the voltage V at its terminals. The electron charge distribution was calculated considering the 2-D electron gas by simultaneously solving the Schrodinger and the Poisson equations, DX centers included. Results from this model predict an asymmetric bell-shape dependence of C on V, with a maximum near the contact potential, and are in good agreement with experiment. This further provides experimental evidence of Γ-Γ and X-X valley coupling for electrons traveling across the heterojunction. For voltage values not too close to the contact potential, it was possible to find a simple method, based on a total depletion, that gives a good fit to experiment