Monte carlo particle simulation of a GaAs MESFET with a gate trench sloping towards the source

A MESFET design with a shallow gate trench that slopes towards the source is proposed. Its characteristics have been simulated by means of the Monte Carlo particle model and compared to those of a planar and uniformly recessed gate structure of similar geometry. The sloped gate should reduce the resistance in the conduction channel and improve the noise figure. It is found that this device combines the good unilateral gain of the planar device and the low intrinsic minimum noise figure of the best uniformly recessed gate transistor. In uniformly recessed gate structures it was found that the length of the gate is important in reducing the noise: by shielding the source field fluctuations from the drain field ones it is possible to reduce the minimum noise figure. The simulation comprises both the DC and the AC characteristics. The latter is obtained around an operating point chosen with the drain biased at saturation. The distributions of fields and carriers for the sloped gate device have been plotted at this point and the equivalent circuit elements extracted.