Numerical simulations of kink phenomena and the related backgating effect in GaAs MESFETs

Two-dimensional simulations of GaAs MESFETs are made in which impact ionization of carriers and deep levels in the semi-insulating substrate are considered. It is shown that the kink or sub-breakdown is explained by impact ionization of holes and the following hole trapping (or hole accumulation) in the substrate rather than by direct gate breakdown. In addition, the kink-related backgating effect is reproduced by our simulation for the first time, and its mechanism is clarified.