Ultrathin LiF Insertion and Ensued Contact Resistance Reduction in MoS2 Channel Transistors

Molybdenum disulfide (MoS2) is a representative 2D n-type semiconductor for various electron devices, but its lateral conduction performances are still restricted, which are mainly attributed to the contact resistance (R-c) in field-effect transistors (FETs). Low-enough R-c value must be realized toward practical device fabrications. Herein, 2D MoS2 FETs using chemical vapor deposited (CVD) MoS2 channels with and without the ultrathin LiF interlayer are fabricated, to demonstrate the practical benefits of LiF. In addition, LiF is also applied to Al metal which is known to be more Earth abundant than Au, expecting the similar positive effects of the inserted LiF. When 35 CVD-grown MoS2 channel FETs with Au are characterized on an identical gate dielectric substrate, the higher value of mobility ranging 55-60 cm(2) V s(-1) is achieved with the inserted LiF than that without LiF (approximate to 20 cm(2) V s(-1)). In the case of another MoS2 FET with exfoliated flake channel and Al contact, its field-effect mobility with LiF insertion appears to be approximate to 35 cm(2) V s(-1), approaching to an almost R-c-free mobility (42 cm(2) V s(-1)).