Phenomenological Model of Gate-Dependent Kink in I-V Characteristics of MoS2 Double-Gate FETs

A phenomenological model, accounting for interface states at metal-semiconductor contacts, is proposed to explain particular gate-bias-dependent kinking in I-V characteristics sometimes observed in MoS 2 FETs. The effect is studied in double-gate FETs by varying top-gate voltage (V TG ) and bottom-gate voltage (V BG ), with the MoS 2 semiconductor layer overlying source/drain (S/D) metal contacts in contact regions. The kink in I D -V TG characteristics is observed for small negative V BG but not for large negative V BG . The model divides the FET into S/D and channel regions, with bias-dependent S/D resistance (R SD ) and channel resistance (R CHAN ), and with S/D regions having an additional interface state distribution (additional to any interface states associated with semiconductor/dielectric interfaces in the channel region) due to an imperfect metal-semiconductor interface where MoS 2 overlies S/D metal. The additional interface states are modeled as a Gaussian distribution of acceptor-like states in the upper region of the semiconductor bandgap. When R SD ≥ R CHAN (V BG less negative), filling of these acceptor-like states as V TG increases creates a kink in I D -V TG characteristics since R SD is a major component of overall resistance limiting drain current, I D . Conversely, when R SD