Negative transconductance in double-gate germanium-on-insulator field effect transistors

Abstract

Transport in double-gate (DG) transistors offers unusual properties due to the coupling between the two channels. We report on room-temperature negative transconductance in germanium-on-insulator DG transistors in the subthreshold regime. The effect is due to the coupling between conducting channels, analogous to the velocity modulation transistor (VMT). Unlike the VMT, our effect can be induced by either of the gates and arises not from a difference in the channel mobilities but from partial electric field screening at low channel densities combined with the density dependence of mobility. The negative transconductance becomes weaker as gate length LG is reduced.