Low Residual Carrier Concentration and High Mobility in 2D Semiconducting BiOSe.

The air-stable and high-mobility two-dimensional (2D) BiOSe semiconductor has emerged as a promising alternative that is complementary to graphene, MoS, and black phosphorus for next-generation digital applications. However, the room-temperature residual charge carrier concentration of 2D BiOSe nanoplates synthesized so far is as high as about 10-10 cm, which results in a poor electrostatic gate control and unsuitable threshold voltage, detrimental to the fabrication of high-performance low-power devices. Here, we first present a facile approach for synthesizing 2D BiOSe single crystals with ultralow carrier concentration of ∼10 cm and high Hall mobility up to 410 cm V s simultaneously at room temperature. With optimized conditions, these high-mobility and low-carrier-concentration 2D BiOSe nanoplates with domain sizes greater than 250 μm and thicknesses down to 4 layers (∼2.5 nm) were readily grown by using Se and BiO powders as coevaporation sources in a dual heating zone chemical vapor deposition (CVD) system. High-quality 2D BiOSe crystals were fabricated into high-performance and low-power transistors, showing excellent current modulation of >10, robust current saturation, and low threshold voltage of -0.4 V. All these features suggest 2D BiOSe as an alternative option for high-performance low-power digital applications.