Control of the Schottky barrier height in monolayer WS2 FETs using molecular doping
Siyuan Zhang, Hsun-Jen Chuang, SON LE, Curt A. Richter, Kathleen McCreary, Berend Jonker, Angela R. Hight Walker, Christina Hacker
The development of processes to controllably dope two-dimensional semiconductors is critical to achieving next generation electronic and optoelectronic devices. Understanding the nature of the contacts is a critical step for realizing efficient charge injection in transition metal dichalcogenides. In this study, post-growth n-doping of chemical vapor deposition grown monolayer (ML) WS2 is achieved by treatment with solutions of molecular reductants. The extent of doping can be conveniently controlled by the concentration of dopant solutions and treatment time. Threshold voltage shifts and tunable channel current are observed in doped WS2 field-effect transistors. This molecular n-doping technique is particularly useful for the selective area doping needed for electrical contacts and reduces the contact resistance (Rc) in ML WS2 by more than two orders of magnitude. The significant reduction of Rc is attributed to the high electron-doping density achieved in WS2 which leads to a significant reduction of Schottky barrier width and height. As a proof-of-concept, following n-doping of monolayer WS2, we achieve high mobility of 97 cm2 V-1 S-1 and high on/off ratio exceeding 106. The dependence of mobility on temperature shows clear evidence of the strong suppression of charge-impurity scattering after the doping. High levels of doping allow the observation of a metal-insulator transition in monolayer WS2 due to strong electron-electron interactions. This doping technique provides a viable route to tailor the electrical properties and improve the contacts in transition metal dichalcogenides, paving the way for high-performance two-dimensional nanoelectronic devices.
, Chuang, H.
, Le, S.
, Richter, C.
, McCreary, K.
, Jonker, B.
, Hight Walker, A.
and Hacker, C.
Control of the Schottky barrier height in monolayer WS2 FETs using molecular doping, AIP Advances, [online], https://doi.org/10.1063/5.0101033, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=934233
(Accessed December 6, 2023)