High-Performance Devices Based on InSe–In_1–xGa_xSe Van der Waals Heterojunctions

Multilayer InSe is a promising material for high-performance optoelectronic applications because of its small direct band gap and good light absorption. However, as a photoconductive photodetector, multilayer InSe photodetectors endure large dark current and high driving power. In this work, we study the electrical properties of InGaSe alloys and demonstrate the high-performance devices based on multilayer InSe–In_0.24Ga_0.76Se van der Waals heterojunctions (vdWHs). The electrical properties of InGaSe alloy samples strongly depend on the ratio of In to Ga, and the In_0.24Ga_0.76Se alloy shows a p-type transport behavior. More importantly, a multilayer InSe–In_0.24Ga_0.76Se vdWH device is demonstrated as a high-performance forward diode, photodiode, and self-powered photodetector (SPPD). The multilayer InSe–In_0.24Ga_0.76Se diode shows a high forward rectification ratio of over 10³ without gate modulation at room temperature, which is superior to most of the multilayer vdWH devices. Moreover, the vdWH photodiode has a broadband photoresponse spectrum (400–1000 nm) and a high-performance photoresponse. The light switching ratio, detectivity (D*), and responsivity (R) are 10³, 10¹² Jones, and 49 A W^–1 for 400 nm illumination, respectively. Furthermore, the vdWH SPPD also shows a sensitive photoresponse to a broadband spectrum of 400–1000 nm. Our work offers an opportunity for multilayer vdWH device applications in high-performance electronic and optoelectronic devices.