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 InSeTe alloys and optoelectronic property of InSe-InSeTep-n heterojunction. The electrical transport properties of InSeTe 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 InSeTe. The p-n InSe-InSeTe 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 InSeTe alloys significantly rely on the ratio of Te/Se and suggests that InSe-InSeTe p-n heterojunction has a excellent potential for application in the self-powered optoelectronic device.