Two-Dimensional Numerical Simulation for GaAs MESFET with Heavy Doping Effects

Abstract

Two-dimensional semiconductor simulation program is a necessary tool for modem semiconductor device design. A new and general simulation program of GaAs MESFET considering heavily doped effects is developed. The effects of heavy doping on the device characteristics of the heavily doped GaAs MESFET are analyzed. It is found that the conventional simulation programs of MESFET face the serious problem of accuracy when the concentration of dopants gets higher. A self-consistent model for describing the electron behaviour in heavily doped semiconductor devices is used. The model allows conveaient treatment of the Poisson's equation, steady-state continuity equations, and transport equations with the heavy doping effects. The bandgap narrowing effects associate with the actual bandgap narrowing effect and the influence of Fermi-Dirac statistics. All the effects are e-Tressed in terms of two band model parameters, the effective bandgap shrinkage, AEp and the effective asymetry fzctor, A. The activity mefficient y can be a useful quantity to represent the nonideality. Two-dimecsional simulation is carried out by taking the heavy doping effects. The results show that the effects have an influence of the increase of the built-in potential. The negative shifts of I-V curve, the slight decrease of transconductance, and the Iittle increase of the threshold voltage are observed as compared to the results of the conventional twodimensional simulation. The Qeneral two-dimensional simulation program can be used well for the design of GaAs and Si MESm circuit of VLSI.