Performance and design of vertical, ballistic, heterostructure field-effect transistors

The influence of ballistic transport and the doping level on the pinch-off voltage in an AlGaAs/GaAs heterostructure permeable base transistor is studied by numerical simulation. It is established that the high velocity of the injected hot electrons prevents a charge build-up in the vertical channel. Therefore, the dependence of the doping on the transconductance is reduced and the doping may, independently, be altered to adjust the pinch-off voltage. These devices are predicted to have an ft above 300 GHz.