Ultrasensitive and Self‐Powered SnSe/Ge Heterojunction Photodetector Driven by Spontaneously Interfacial Excitation Transfer of Carriers

Abstract Binary chalcogenide semiconductor of SnSe with layer‐by‐layer phase opens up new opportunities for construction of versatile nanoelectronics and optoelectronics devices. The superior crystal properties make the layered SnSe compatible with traditional microfabrication techniques. Although several significant dynamic processes of carriers on 2D SnSe/Ge interface can be responsible for low‐dissipation devices with higher quantum efficiency, the controlled growth and photodetection application of SnSe/Ge heterojunction have rarely been investigated. Herein, the high‐quality 2D SnSe/Ge heterostructure with electronically abrupt interface is designed for the first time. A prominent photoluminescence quenching behavior is observed attributing to spontaneously interlayer transfer of long‐lived carriers under optical excitation. It is confirmed to be attractive for development of self‐powered photodetectors. Then, the ultrasensitive SnSe/Ge photodetector is explored, which shows a higher photocurrent up to 1.22 mA under 1064 nm illumination at 0.0 V. Meanwhile, it presents an obtainable responsivity of 0.51 A W⁻¹, larger detectivity of 1.51 × 10¹¹ Jones, and ultrashort response time of 5.47 µs in self‐driven mode. The study provides a profound understanding of interlayer excitation transfer mechanisms of long‐lived carriers inside SnSe/Ge heterojunction. The newly‐developed photodetector provides an essential step toward meeting the ever‐increasing demand for ultrafast and low‐dissipation optoelectronic devices.