Ternary MoSe_2xTe_2-2x alloy with tunable band gap for electronic and optoelectronic transistors

Two-dimensional transition metal dichalcogenide (2D TMDs) alloys, consisting of three or more elements, offer a luxury variety of chemical and physical properties through elemental ratio alteration, thus may provide ideal candidate with tunable band gap for specific electrical applications. In this work, we demonstrate a high-quality layered MoSe_2xTe_2-2x (x = 0 ∼ 1) alloy synthesized via one-step chemical vapor transport method for high-performance electronic and optoelectronic transistors. Our characterizations reveal the obtained ternary alloy forming high-quality single crystal layers with 2H phase. Interestingly, the electronic transistors fabricated on MoSe_2xTe_2-2x thin layers (6 ∼ 7 layers) display an anomalous transition from ambipolar to n-type in conductive characteristics with the increase of substitution x value. The subsequent photoelectrical measurements exhibit that high on-off ratio for every ratio (x = 0.18, 0.38, 0.67, 0.83) with optical band gap in the range of 1.6 eV and 1.1 eV (near infrared). The optimized MoSe_0.37Te_1.63-based transistor can achieve up to ∼10⁷ I _on/I _off and 10⁵ I _ph/I _dark ratio, 100 mA W^-1 photo-responsivity and 2.38% external quantum efficiency with high photoresponsivity. Thus, such ternary MoSe_2xTe_2-2x alloys may pose a great potential for 2D-based electronic and photoelectronic applications.