Differential capacitance as a method of determining the presence of a quasi-bidimensional electronic gas

Abstract

We present the differential capacitance profile for the delta-doped field effect transistor (δ-FET) in a GaAs matrix with both the presence and absence of a two-dimensional electronic gas produced by the delta-doped quantum well. We demonstrate that in the absence of any quantum well a background impurities concentration greater than the real one is obtained when the traditional C–V method is used. If there exist a two-dimensional electronic gas, the background impurity concentration obtained would be less than the real one. The use of this experimental method allows to reveal the presence of electronic confinement in these systems. We propose a simple model, providing the shape of the conduction band for this particular case, as well as the depletion region width used to calculate the differential capacitance. It is seen that the proposed model is useful for extracting information concerning this kind of system.