Use of two-dimensional process and device modeling to solve some real problems in GaAs MESFET design and analysis

A new, easy-to-use two-dimensional Poisson solver, GATES-2d, is described. The program is used to address two problems that only a two-dimensional simulator can answer: the problem of simultaneously minimizing short-channel effects, source resistances, and fringe capacitances in self-aligned MESFET technology, and analyzing parasitic capacitances in recess-etched technology. Poisson´s equation is solved for the electron concentration n(x,y) (assumed to obey Boltzmann statistics) in the presence of shallow donors and acceptors and deep donors (EL2) and acceptors (Cr). 2D piezoelectric and surface-potential effects are included. With the results, analytical calculations are made of sheet resistances and saturated current at every vertical slice. The total capacitance is computed by integrating the electron concentration over the region simulated, and taking twice the (half-FET) change with gate voltage.<>