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

• Published in: Nature nanotechnology Vol. 15; no. 8; pp. 675 - 682
• Main Authors: Lukman, Steven, Ding, Lu, Xu, Lei, Tao, Ye, Riis-Jensen, Anders C., Zhang, Gang, Wu, Qing Yang Steve, 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
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.08.2020; Nature Publishing Group
• Subjects: 639/301/1005/1007; 639/301/357/1018; Chemistry and Materials Science; Crystal growth; Excitons; Hafnium; Hafnium compounds; Heterostructures; High temperature; Infrared radiation; Interlayers; Low temperature; Materials Science; Materials selection; Nanotechnology; Nanotechnology and Microengineering; Operating temperature; Optical transition; Photometers; Room temperature; Temperature; Tungsten; Tungsten disulfide; Two dimensional materials
• ISSN: 1748-3387; 1748-3395; 1748-3395
• DOI: 10.1038/s41565-020-0717-2

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, WS 2 /HfS 2 . 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 WS 2 /HfS 2 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. Formation of interlayer excitons with high oscillator strength in a WS 2 /HfS 2 heterostructure enables the realization of high-responsivity room-temperature mid- and long-wavelength infrared photodetectors.