A finite-element program for modeling transient phenomena in GaAs MESFET's

A two-dimensional finite-element program has been developed for analyzing transient and steady-state characteristics of GaAs devices with arbitrary geometric boundary shapes. The program code consists of two separate programs, GRID and FET, which are discussed in some detail. GRID serves to generate a nonuniform mesh, while FET computes a self-consistent solution of Poisson's and the current continuity equations. A GaAs FET with a trapezoidal recessed gate structure has been studied to demonstrate the capabilities of the program to analyze odd shapes. Current-voltage characteristics were computed for the recessed gate and a planar device. The results from both FET structures are compared and analyzed. In particular the effect of the recessed gate on the field distribution in the device is discussed. Large signal transient behaviors of both devices were examined, and it was found that both device structures produce similar results in steady-state and transient conditions.