Ultrasensitive negative photoresponse in 2D Cr2Ge2Te6 photodetector with light-induced carrier trapping

Abstract

Cr₂Ge₂Te₆, a layered ferromagnetic semiconductor, has triggered extensive research interest due to its fantastic ferromagnetism and semiconducting characteristics as well as potential applications in next-generation spintronic and nanoelectronic devices. On the basis of its ferromagnetism, combined with rich electronic and optical properties, Cr₂Ge₂Te₆ could be a promising candidate for optoelectronics including magnetophotonics and photodetectors. However, there are no relevant studies addressing this to date. In this work, we comprehensively investigated the photoresponse characteristics of few-layer Cr₂Ge₂Te₆-based detectors. An uncommon negative photoconductivity (NPC) and correlated mechanism are explored with the Cr₂Ge₂Te₆ photodetector. It is found that, both NPC and positive photoconductivity (PPC) may exist in an individual Cr₂Ge₂Te₆ device, which are adjustable by control of the incident light intensity. More significantly, the NPC behavior enables ultrasensitive photoresponses of the Cr₂Ge₂Te₆ photodetectors, where the detection of a weak light with an incident power intensity as low as 0.04 pW and a high responsivity of 340 AW^-1 is achieved. This extraordinary performance demonstrates that the two-dimensional (2D) Cr₂Ge₂Te₆ holds great promise for applications in ultraweak light detection.