Excitons are electron-hole pairs bound by Coulombic forces. Serving as a bridge between optical and electrical signals, excitonic devices have great potential in integrated optoelectronic chips. The early development of excitonic devices was mainly based on traditional inorganic semiconductor materials, utilizing semiconductor quantum well structures to induce exciton generation and realizing exciton-based transistor devices with short-range transport. However, the binding energy of excitons in such semiconductor quantum well systems is small, and corresponding excitonic devices typically need to operate in the liquid helium temperature range, which greatly hinders their practical applications. In recent years, thanks to the higher exciton binding energy of two-dimensional (2D) transition metal dichalcogenides (TMDCs), excitonic devices based on 2D monolayer semiconductors have a better chance of operating at room temperature and are expected to be applied in the field of high-speed optoelectronic signal conversion. However, achieving high-speed electrical modulation of exciton distribution in monolayer semiconductors at room temperature still poses significant challenges.
Recently, the group of Prof. Wei Du and Prof. Tao Wang of our institute designed an excitonic device based on Au-TMDC-Au lateral junction. By applying high-frequency AC bias to the two metal electrodes, they can achieve high speed electrical modulation of the in-plane excitonic distribution in the monolayer semiconductor at room temperature. Under the lateral electric field, the trap states at the Au/TMDC interface can capture or release charges, thereby changing the distribution of carrier concentrations in the monolayer semiconductor, as well as the exciton-charge interaction, thus generating effective excitonic modulation. Moreover, this strategy is suitable for different types of TMDC materials, and the modulation signal is related to the doping type and doping level of the monolayer semiconductor. It is worth noting that the switching time for the excitonic modulation in this device is down to 5 nanoseconds, which lays the foundation for further development of high-speed electrically driven excitonic devices in the future. This study reveals the application of trap-assisted exciton modulation in 2D monolayer semiconductors and provides new ideas for the development of room-temperature excitonic devices and optoelectronic chips.
Link：https://www.nature.com/articles/s41467-023-42568-w
Authors：Guangpeng Zhu, Lan Zhang, Wenfei Li, Xiuqi Shi, Zhen Zou, Qianqian Guo, Xiang Li, Weigao Xu, Jiansheng Jie, Tao Wang*, Wei Du*, Qihua Xiong
Editor: Guo Jia