Source/Drain Doping Effects and Performance Analysis of Ballistic III-V n-MOSFETs

Effects of source/drain (S/D) doping density (N_SD) on the ballistic performance of III-V nanowire (NW) n-channel metal-oxide-semiconductor field-effect transistors (n-MOSFETs) are explored through atomistic quantum transport simulation. Different III-V materials (InAs, GaAs) and transport directions (<;100>, <;110>) are considered with Si included for benchmarking for a gate length of 13 nm. For III-V´s, depending on the operating condition (OFF-current target for a given supply voltage), there exists an optimum N_SD that maximizes ON-current (I_ON) by balancing source exhaustion versus tunneling leakage. For InAs, sub-threshold swing degrades significantly with increasing N_SD due to the light effective mass (m*) and source-drain tunneling, so the optimum N_SD is low. For GaAs, such dependence is much weaker due to the larger m*, and the optimum N_SD is higher. With optimized N_SD´s, InAs shows low ballistic I_ON due to the low density-of-state (DOS) whereas GaAs NW with <;110> transport direction shows good ballistic I_ON due to the improved DOS with still high injection velocity, making it a better candidate for high performance device.