The effects of doping, gate length, and gate dielectric on inverse subthreshold slope and on/off current ratio of a top gate silicon nanowire transistor

The effects of gate length L_g, gate dielectric constant isin_ox, gate oxide thickness tox, and sourc/drain doping concentration on inverse subthreshold slope and on/off current ratio of a top gate silicon nanowire on insulator device are studied using three dimensional quantum simulation. The variation of inverse subthreshold slope and on/off current ratio are very sensitive to gate length, gate dielectric constant, and oxide thickness and relatively less sensitive to doping concentration. Significant improvement in subthreshold slope and on/off current ratio can be achieved using high-K gate dielectric with thinner oxide and relatively longer gate. The key feature of this improvement is the better gate control of channel potential with longer L_g, higher isin_ox, and thinner t_ox. Due to better control of channel potential, the tunneling current through the conduction band is significantly suppressed in the subthreshold regime that improves the subthreshold slope and on/off current ratio.