Microplasma and uniform MESFET gate breakdown

On the basis of 2-D numerical simulation the mechanism of "microplasma" and "uniform" gate-drain breakdown in the GaAs MESFET's is studied. It is stated that when the MESFET design provides the negative differential conductivity of the part of channel between the gate and the drain recess edge the avalanche current distribution is unstable and microplasma, as a solitary avalanche current filament, is exited at some critical avalanche current. The universal mechanism of microplasma breakdown in semiconductor structures is suggested.