Two-dimensional numerical simulation of trapping phenomena in the substrate of GaAs MESFET's

A two-dimensional physical model which includes the effects of deep levels in semi-insulating GaAs is described and applied to an investigation of the effects of trapping phenomena in the substrate of a GaAs MESFET. The model is used to investigate some of the anomalous features of the operation of these devices which have in the past been attributed to traps near the channel-substrate interface. The mechanisms by which deep levels determine the detail of the transient behavior under pulsed operation is determined. In addition, the frequency dependence of the output conductance is explained in terms of a reduction in the magnitude of the substrate current at low frequencies as the trap filling varies in response to the impressed terminal voltages. The calculations reported are supported by experimental measurement of a similar device.<
>