Tunable Photoinduced Carrier Transport of a Black Phosphorus Transistor with Extended Stability Using a Light-Sensitized Encapsulated Layer

In this article, we propose a novel approach to demonstrate tunable photoinduced carrier transport of a few-layered black phosphorus (BP) field-effect transistor (FET) with extended air stability using a “light-sensitized ultrathin encapsulated layer”. Titanium suboxide (TiO_x) ultrathin film (approximately 3 nm), which is an amorphous phase of crystalline TiO₂ and can be solution processed, simultaneously exhibits the unique dual functions of passivation and photoinduced doping on a BP FET. The photoinduced electron transfer at TiO_x/BP interfaces provides tunable n-type doping on BP through light illumination. Accordingly, the intrinsic hole-dominated transport of BP can be gradually tuned to the electron-dominated transport at a TiO_x/BP FET using light modulation, with enhanced electron mobility and extended air stability of the device. The novel device structure consisting of a light-sensitized encapsulated layer with controllable and reversible doping through light illumination on BP exhibits great potential for the future development of stable BP-based semiconductor logic devices or optoelectronic devices.