Gate-drain avalanche breakdown in GaAs power MESFET´s

The voltage breakdown behavior of a number of different MESFET structures has been investigated using a two-dimensional numerical model. The site of the avalanche is found to be under the drain edge of the gate in recessed devices under all bias conditions, but moves towards the drain contact in planar structures when the channel is not pinched off. The dependence of the breakdown voltage on a variety of geometrical and physical variables has been studied. In particular the surface is shown to play an important part in determining the breakdown voltage.