The current density distribution of the GaAs power MESFET: a theory for device burnout

The burnout of a GaAs power MESFET is initiated at the edge of the drain ohmic contact due to the high local current density. A two-dimensional Poisson equation is solved to obtain the current density distribution under the drain. The maximum current density is found to be proportional to the drain current and inversely proportional to the thickness of the active layer under the drain. The burnout voltage can therefore be improved by adding a gate recess to allow a thicker active layer under the drain