MOSFET's negative transconductance at room temperature

Negative transconductance is reported for the first time at T=300 K for NMOS transistors fabricated with different technologies and oxide thickness in the 3-20 nm range. The effects of drain bias, channel length, oxide thickness as well as substrate doping and bias on the phenomenon are investigated. The results are interpreted in terms of surface-roughness limited mobility, and parameters for mobility modeling at high effective fields are extracted.