Kink effect related to the self-side-gating effect in GaAs MESFET's

A kink effect, an abrupt increase in drain current at high drain voltages, was observed in GaAs MESFET's with an Al/sub 0.2/Ga/sub 0.8/As/GaAs heterostructure buffer layer. In these MESFET's, impact ionization occurs at the drain side along the channel current path at high drain voltages. On the other hand, a side-gating effect occurs when a negative voltage applied to the gate pad of the MESFET (self-side-gating effect). From measurements of the substrate potential, we conclude that hole accumulation generated by the impact ionization at the channel-side GaAs/Al/sub 0.2/Ga/sub 0.8/As interface cancels the drain current reduction that arises from the self-side-gating effect. This gives rise to the kink effect we observe. >