Achieving Ambipolar Transport Characteristics in the n-WS2 Channel via Remote p-Doping and its Enhancement-Mode Ambipolar Field-Effect Transistor Operation

Abstract

To overcome the inherent short-channel effects in Si microelectronics and enhance the performances of ultrahigh-density integrated circuits, researchers are focused on developing next-generation channel materials compatible with Si industry standards. Ambipolar two-dimensional (2D) transition metal dichalcogenides (TMDs), such as WS₂, exhibit great promise due to their layer-dependent bandgaps and highly comparable carrier mobilities for both holes and electrons. However, the prevalence of defects in WS₂, particularly chalcogen vacancies, often results in n-dominant behavior, restricting ambipolar transport. For the integration of n-WS₂ into Si-based complementary metal-oxide semiconductor (CMOS) platforms, reliable hole-doping techniques are essential to achieve comparable hole and electron transports. Herein, we introduce a remote charge-transfer doping approach to enable the stable hole-doping of n-WS₂ while maintaining its electron-conductive properties. Using WSe₂ as the separation layer and WO_x for remote p-doping, we achieve enhancement-mode ambipolar WS₂/WSe₂–WO_x heterostructure field-effect transistors (FETs). The fabricated ambipolar WS₂/WSe₂–WO_x FETs demonstrate comparable field-effect carrier mobilities (hole: 267 cm²/V s and electron: 13.6 cm²/V s) and current on/off ratios (hole: ∼1 × 10⁸ and electron: ∼1 × 10⁷). These results highlight the stable operational characteristics of the device and underscore the potential of 2D materials to reduce the footprint of the CMOS architecture and simplify the complex CMOS fabrication process.