On-Off Charge-Voltage Characteristics and Dopant Number Fluctuation Effects in Junctionless Double-Gate MOSFETs

Junctionless double-gate (DG) MOSFETs are assessed by analyzing the on-off characteristics of the mobile charge density as a function of gate voltage. Compared with undoped DG MOSFETs, junctionless MOSFETs have an inferior on-off charge performance with more degradation at higher doping. The results also indicate a major issue: dopant number fluctuations in minimum width junctionless MOSFETs. A first-order analytic expression shows that the one-sigma threshold fluctuation is proportional to the square root of doping concentration. Inclusion of the quantum effect makes no significant difference to the results.