In this paper, a simple and accurate analytical model for current–voltage and small-signal characteristics of AlmGa1_mN/GaN modulation doped field-effect transistor (MODFET) devices is presented. For the charge control model, Fermi potential variation with sheet carrier concentration, the infiltration of a two-dimensional electron gas wave function into the spacer layer, and the effects of spontaneous and piezoelectric polarizations at the heterointerface are considered. Also, parasitic source/drain resistances have been incorporated in the analysis. In addition, a suitable drift velocity model and the gate voltage dependence of low-field mobility are used to provide simple and accurate equations for the different characteristics of AlGaN/GaN MODFET devices. By implementing the model in the MATLAB environment, current–voltage characteristics, transconductance, output conductance, capacitance–voltage characteristics, and cutoff frequency have been calculated. A comparison of simulation results with published experimental data for Al0:15Ga0:85N/GaN shows excellent agreement, thereby proving the validity of the model.

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