Hole mobility enhancement in monolayer WSe2 p-type transistors through molecular doping

Abstract

Two-dimensional (2D) transition metal dichalcogenide (TMDC) semiconductor materials exhibit extraordinary electrical properties, holding promise for the realization of next-generation complementary metal-oxide-semiconductor (CMOS) devices at ultimate scaling. However, constrained by effective device doping strategies, the hole mobility and device performance of tungsten diselenide (WSe₂) p-type transistors, especially monolayer chemical vapor deposition (CVD)-grown WSe₂, have not met expectations. In this paper, an effective performance enhancement of monolayer WSe₂ p-type transistor was achieved through a molecular doping strategy. Synthesizing monolayer WSe₂ directly on SiO₂ back-gated substrates and leveraging energy band alignment design, 4-nitrobenzenediazonium tetrafluoroborate (4-NBD) molecular dopant with a concentration of 10 mM was utilized to modulate the Fermi level position of monolayer WSe₂ for hole doping. The devices demonstrated a more than 98% increase in hole mobility, reaching up to 97 cm² · V⁻¹ · s⁻¹ while maintaining the current on/off ratio of 10⁸. Monolayer p-type WSe₂ transistors with 1 µm channel length exhibit a high drive current surpassing 176 µA · µm⁻¹, exceeding previous CVD-WSe₂ devices with similar channel length. This straightforward and effective approach to improving the electrical performance of WSe₂ transistors paves the way for advanced logic technologies based on transition metal dichalcogenide semiconductors.