A theoretical study of the high frequency performance of a Schottky barrier field effect transistor fabricated on a high resistivity substrate

The short circuit admittance parameters for a silicon Schottky barrier field effect transistor fabricated on a high resistivity substrate are calculated from first principles ignoring the effects of minority carriers. The results of these calculations are valid to frequencies beyond the maximum frequency of oscillation of the device, which for the structure considered was about 18 GHz. The calculated admittance parameters are shown to be in good agreement with published experimental data. In order to describe the dynamic behavior of the device the static properties must first be obtained. The simultaneous solution of Poisson's equation and the continuity equation, both in two dimensions, gives the static charge and potential distribution in the device. The effects of a field dependent mobility are included in the continuity equation which is formulated in terms of the quasi-fermi level. Using the results of static two dimensional solutions, a one dimensional device model is developed which permits the dynamic device behavior to be described by a one dimensional linear ordinary differential equation. By solving this equation under appropriate boundary conditions the device y-parameters are found as functions of frequency. Calculated results will be compared with published experimental data and the sources of the deviations which exist will be discussed.