Tunable electronic properties of multilayer InSe by alloy engineering for high performance self-powered photodetector

Multilayer indium selenide (InSe) is a good candidate for high performance electronic and optoelectronic devices. The electrical performance of InSe is effectively regulated by dielectric layers, contact electrodes and surface doping. However, as a powerful tool to tune properties of materials, alloy engineering is absent for multilayer InSe. In this letter, for the first time, we investigate the electrical property of InSe_1-xTe_x alloys and optoelectronic property of InSe-InSe_0.82Te_0.18p-n heterojunction. The electrical transport properties of InSe_1-xTe_x alloys strongly depend on the content of Te composition. With the ratio of Te/Se increasing, the n-type electron transport behavior of InSe gradually transfers to the p-type hole transport behavior of InSe_0.82Te_0.18. The p-n InSe-InSe_0.82Te_0.18 heterojunction shows a rectification effect and a self-powered photodetection. The self-powered photodetector (SPPD) has a broad photodetection range from visible light (400 nm) to near-infrared (NIR) light (1000 nm). The responsivity (R) of SPPD is 14.1 mA/W under illuminated by NIR light (900 nm) at zero bias, which is comparable to some of the 2D heterojunctions NIR photodetectors measured with an external bias. The SPPD also shows a stable and fast response to NIR light (900 nm). This work demonstrates that the electrical transport properties of InSe_1-xTe_x alloys significantly rely on the ratio of Te/Se and suggests that InSe-InSe_1-xTe_x p-n heterojunction has a excellent potential for application in the self-powered optoelectronic device.