Subthreshold conduction in uniformly doped epitaxial GaAs MESFETs

The channel gating function that determines the conducting cross section of the channel is calculated for the case of a uniformly doped epitaxial GaAs metal-semiconductor field-effect transistor (MESFET) by solution of the Poisson-Boltzmann equation for the n-layer/buffer (substrate) interface. This analysis improves on the depletion approximation by including the interaction between the depletion-edge transition regions of the gate and of the substrate space charge, thus providing a more accurate description of the carrier distribution in the channel for cases near to or into the pinchoff region. An analytical model is derived from the numerical results, and good agreement is found between this model and experimental devices