Stable and Reversible Triphenylphosphine-Based n-Type Doping Technique for Molybdenum Disulfide (MoS₂)

A highly stable and reversible n-type doping technique for molybdenum disulfide (MoS₂) transistors and photodetectors is developed in this study. This doping technique is based on triphenylphosphine (PPh₃) and significantly improves the performance of MoS₂ transistor and photodetector devices in terms of the on/off-current ratio (8.72 × 10⁴ → 8.70 × 10⁵), mobility (12.1 → 241 cm²/V·s), and photoresponsivity (R) (2.77 × 10³ → 3.92 × 10⁵ A/W). The range of doping concentrations is broadly distributed between 1.56 × 10¹¹ and 9.75 × 10¹² cm^-2 and is easily controlled by adjusting the temperature at which the PPh₃ layer is formed. In addition, this doping technique provides two interesting properties that have not been reported for previous molecular doping techniques: (i) high stability leading to small variations in device performance after exposure to air for 14 days (on-current: 1.34% and photoresponsivity: 1.58%) and (ii) reversibility enabling the repetitive formation and removal of PPh₃ molecules (doping and dedoping).