Spatially Bandgap-Graded MoS2(1−x)Se2x Homojunctions for Self-Powered Visible–Near-Infrared Phototransistors

• Main Authors: Hao Xu, Juntong Zhu, Guifu Zou, Wei Liu, Xiao Li, Caihong Li, Gyeong Hee Ryu, Wenshuo Xu, Xiaoyu Han, Zhengxiao Guo, Jamie H. Warner, Jiang Wu, Huiyun Liu
• Format: Article
• Language: English
• Published: SpringerOpen 2020-01-01
• Series: Nano-Micro Letters
• Subjects: Transition metal dichalcogenides; Graded bandgaps; Homojunctions; Phototransistors; Self-powered
• Online Access: https://doi.org/10.1007/s40820-019-0361-2

Abstract Ternary transition metal dichalcogenide alloys with spatially graded bandgaps are an emerging class of two-dimensional materials with unique features, which opens up new potential for device applications. Here, visible–near-infrared and self-powered phototransistors based on spatially bandgap-graded MoS2(1−x)Se2x alloys, synthesized by a simple and controllable chemical solution deposition method, are reported. The graded bandgaps, arising from the spatial grading of Se composition and thickness within a single domain, are tuned from 1.83 to 1.73 eV, leading to the formation of a homojunction with a built-in electric field. Consequently, a strong and sensitive gate-modulated photovoltaic effect is demonstrated, enabling the homojunction phototransistors at zero bias to deliver a photoresponsivity of 311 mA W−1, a specific detectivity up to ~ 1011 Jones, and an on/off ratio up to ~ 104. Remarkably, when illuminated by the lights ranging from 405 to 808 nm, the biased devices yield a champion photoresponsivity of 191.5 A W−1, a specific detectivity up to ~ 1012 Jones, a photoconductive gain of 106–107, and a photoresponsive time in the order of ~ 50 ms. These results provide a simple and competitive solution to the bandgap engineering of two-dimensional materials for device applications without the need for p–n junctions.