Beyond-punchthrough current in GaAs MESFET's

In a recent letter published in this journal, Patrick et al. reported on a maximum drain voltage for pinchoff Which varied exponentially with gate length in very short-gate GaAs MESFET's. The I-V characteristics given showed that this variation is associated with beyond-punchthrough drain current. Current flowing across a depleted region is an instance of the triode mode of FET operation described by other researchers in 1966. Triode-mode theory can help in the understanding of the behavior of GaAs MESFET's near pinchoff, including the devices of Patrick et al.