High oscillator strength interlayer excitons in two-dimensional heterostructures for mid-infrared photodetection

• Main Authors: Lukman, Steven, Ding, Lu, Xu, Lei, Tao, Ye, Riis-Jensen, Anders C., Zhang, Gang, Wu, Steve Qing Yang, Yang, Ming, Luo, Sheng, Hsu, Chuanghan, Yao, Liangzi, Liang, Gengchiau, Lin, Hsin, Zhang, Yong-Wei, Thygesen, Kristian S., Wang, Qi Jie, Feng, Yuanping, Teng, Jinghua
• Other Authors: School of Electrical and Electronic Engineering
• Format: Article
• Language: English
• Published: 2020
• Subjects: Engineering::Electrical and electronic engineering; 2D materials; 2D heterostructure
• Online Access: https://hdl.handle.net/10356/144025
• Institution: Nanyang Technological University

The development of infrared photodetectors is mainly limited by the choice of available materials and the intricate crystal growth process. Moreover, thermally activated carriers in traditional III-V and II-VI semiconductors enforce low operating temperatures in the infrared photodetectors. Here we demonstrate infrared photodetection enabled by interlayer excitons (ILEs) generated between tungsten and hafnium disulfide, WS2/HfS2. The photodetector operates at room temperature and shows an even higher performance at higher temperatures owing to the large exciton binding energy and phonon-assisted optical transition. The unique band alignment in the WS2/HfS2 heterostructure allows interlayer bandgap tuning from the mid- to long-wave infrared spectrum. We postulate that the sizeable charge delocalization and ILE accumulation at the interface result in a greatly enhanced oscillator strength of the ILEs and a high responsivity of the photodetector. The sensitivity of ILEs to the thickness of two-dimensional materials and the external field provides an excellent platform to realize robust tunable room temperature infrared photodetectors.