Tellurium/MoS₂ heterojunction for wavelength-tunable polarity self-driven photodetector and optically switchable inverter

Heterostructures with the configuration of two-dimensional (2D) p-n type semiconductors have been widely studied since they not only combine the advantages of the constituent materials, but also generate new phenomena, such as the formation of built-in electric fields that help separate photogenerated carriers, suppress dark current to improve the sensitivity of photodetector, and exhibit negative differential transconductance (NDT). Inspired by these works, we have chosen the emerging p-type semiconductor tellurium (Te), which has excellent air stability and can be used for infrared photodetection, and the typical n-type semiconductor MoS₂, to form a heterojunction. Due to the built-in electric field between Te and MoS₂, as well as the formation of Schottky barrier between Te and electrode materials, the device exhibits negative/positive photoresponse under visible and infrared light, respectively, without external bias, showcasing the potential for optical encoding communication. Moreover, this self-driven photodetector performs the photoresponsivities of 1.51 A/W and 642.92 mA/W under 520 nm and 1550 nm illumination, respectively, with millisecond level response speeds. In addition, the Te/MoS2 heterostructure displays the NDT phenomena which can be used to implement as a simple CMOS inverter and the inverter can be turned off under illumination. In summary, our work has achieved wavelength-tunable positive /negative optical response as well as light switchable inverters on devices with the same structure, promoting the compactness of integrated components and expanding research on Te and its application fields.