Ultra‐Thin GeSe/WS2 Vertical Heterojunction with Excellent Optoelectronic Performances

Abstract

AbstractHeterostructural engineering of atomically thin 2D materials offers an exciting opportunity to fabricate atomically sharp interfaces for optoelectronic devices. Herein, GeSe/WS2 heterojunction devices composed of 2D WS2 (n‐type) and few‐layer GeSe (p‐type), are fabricated by transferring mechanically exfoliated GeSe to chemical vapor deposition (CVD)‐grown WS2. Excellent rectification behavior is observed from the I−V characteristics of the GeSe/WS2 heterojunction devices. The reverse photocurrent increases more rapidly than the forward photocurrent under a 635 nm laser illumination, indicating an effective separation of the photogenerated carriers under a minus bias. A large photocurrent on‐off ratio of 103 at −5 V bias, a high responsivity (Rλ) of 1.1 A W−1, a considerable specific detectivity (D*) of 1.3×1010 Jones, and a high external quantum efficiency (EQE) of 214.8%, are obtained. Owing to the large built‐in potential of the heterojunction, efficient charge transfer is achieved from the abrupt interfaces even though vastly different materials are used in the van der Waals (vdW) heterostructure. A convenient route is demonstrated for the preparation of ultra‐thin GeSe/WS2 vdW heterojunctions. The results reveal great potential of the present GeSe/WS2 vertical heterojunction for future applications in optoelectronics.