On the Determination of Charge Profiles in Epitaxial Layers of ZnSe by Capacitance Measurements

The doping profile in semiconducting epitaxial layers is often deduced from the behavior of the capacitance of a Schottky contact evaporated onto the surface of the layer as a function of the bias voltage. It is shown on the example of Au/ZnSe/GaAs heterostructures that the heterojunction with the substrate in series with this Schottky contact leads to erroneous profiles, if no special care is taken in the choice of the frequency used in measuring the capacitance. This frequency must be chosen below the cutoff frequency which is apparent in the graphs of the capacitance vs the frequency.