A Bifunctional Optoelectronic Device for Photodetection and Photoluminescence Switching Based on Graphene/ZnTe/Graphene van der Waals Heterostructures.

Controlling the dynamic processes, such as generation, separation, transport, and recombination, of photoexcited carriers in a semiconductor is foundational in the design of various devices for optoelectronic applications. One may imagine that if different processes can be manipulated in one single device and thus generate useful signals, a multifunctional device can be realized, and the toolbox for integrated optoelectronics will be expanded. Here, we revealed that in a graphene/ZnTe/graphene van der Waals (vdW) heterostructure, the carriers can be generated by illumination from visible to infrared frequencies, and thus, the detected spectrum range extends to the communication band, well beyond the band gap of ZnTe (2.26 eV). More importantly, we are able to control the competition between separation and recombination of the photoexcited carriers by an electric bias along the thickness-defined channel of the ZnTe flake: as the bias increases, the photodetecting performance, e.g. response speed and photocurrent, are improved due to the efficient separation of carriers; synchronously, the photoluminescence (PL) intensity decreases and even switches off due to the suppressed recombination process. The ZnTe-based vdW heterostructure device thus integrates both photodetection and PL switching functions by manipulating the generation, separation, transport, and recombination of carriers, which may inspire the design of the next generation of miniaturized optoelectronic devices based on the vdW heterostructures made by various thin flakes.