The intrinsic n-type behavior and unavailability of the appropriate p-type doping method for MoS2 allows only n-type conduction with depletion mode (D-mode) characteristics and forbids the implementation of p-type field-effect transistors (FETs). The D-mode characteristic results in a high off-current (IOFF) at zero gate bias, which limits the usage of MoS2 FETs for industry-scale (n-channel metal-oxide semiconductor) NMOS/(complementary metal-oxide semiconductor) CMOS-logic-based applications due to significant power dissipation. Both these issues, i.e., i) missing technique for p-type doping and ii) D-mode operation are addressed here through the application of argon (Ar) plasma and subsequent O2 bath. Here, Ar plasma results in the physical removal of sulfur (S) atoms from the MoS2 surface, introducing sulfur vacancies, and the O2 bath results in the chemical bonding of O2 molecules with molybdenum (Mo) atoms at the introduced S vacancy sites. This leads to the formation of shallow acceptor states near the valance band (VB) of MoS2, resulting in p-type doping and enhancement mode (E-mode) characteristics of MoS2 FETs. Moreover, using Ar plasma results in the reduction of contact resistance (RC) of E-mode MoS2 FETs and hence facilitates achieving high-performance top-gated E-mode MoS2 FETs with IOFF (at zero gate bias) in tens of picoamperes and ION/IOFF in seven orders.
Keywords: MoS2 FET contact resistance improvement; MoS2 plasma treatment; MoS2 p‐type doping; MoS2‐based NMOS inverter; density functional theory; enhancement‐mode MoS2 FET.
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