Negative differential conductivity and isothermal drain breakdown of the GaAs MESFET

Electrical breakdown in GaAs MESFET's is simulated by two-dimensional (2-D) quasi hydrodynamic isothermal model with two types of carriers and "mixed" boundary conditions on the contacts-fixed drain current and fixed gate bias. It was demonstrated, that when some maximum drain voltage is reached the MESFET's differential conductivity becomes negative at every gate bias. The negative differential conductivity (NDC) is caused by the electric field reconstruction in the buffer by the injected carrier space charge. It is shown that the suggested breakdown model corresponds to the experimentally observed properties of the drain breakdown of the GaAs MESFET. The instantaneous burnout of the GaAs MESFET at the drain breakdown is explained by the uncontrollable drain current increase due to the NDC formation.