Wafer-scale CVD Monolayer WSe<sub>2</sub> p-FETs with Record-high 727 μA/μm I<sub>on</sub> and 490 μS/ μm g<sub>max</sub> via Hybrid Charge Transfer and Molecular Doping
Hao-Yu Lan, Rahul Tripathi, Xiangkai Liu, Joerg Appenzeller, Zhihong Chen
Abstract
This study introduces a novel hybrid p-doping strategy, integrating tungsten oxide (WO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> ) charge transfer and nitric oxide (NO) molecular doping with wafer-scale CVD grown monolayer tungsten diselenide (1L-WSe <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> ). This hybrid doping approach has enabled a record-high on-current I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</inf> of 727 μA/μm at a V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DS</inf> of -1.5 V and a record-high transconductance (g <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</inf> ) of 490 μS/μm, while maintaining an excellent on-off current ratio of ~ 9 orders of magnitude in wafer-scale CVD 1L-WSe <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> p-FETs. We fabricated field-effect transistors in which 1L-WSe <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> is encapsulated by its native oxide WO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> interfacial layer (IL). Analogous to the role of SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> IL in Si CMOS, the native oxide WO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> IL can effectively preserve intrinsic channel properties and allow for threshold voltage (V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</inf> ) tuning without compromising the on-off ratio. Furthermore, nitric oxide (NO) molecular doping was employed to further shift V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</inf> for p-type doping. Unlike most reported doping techniques, NO doping improves the device on-current as well as the subthreshold swing (SS), without sacrificing the on-off ratio. This pioneering hybrid doping scheme could lay the foundation for the development of high-performance PMOS devices based on 2D WSe <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> .