Millimeter-Sized Layered GeI₂ Single Crystals as a Promising Platform for Broadband Photodetectors

Abstract

In the modern era, the limitations of conventional semiconductors have prompted the increasing importance of highquality layered materials for high-performance (opto)electronic devices. Herein, we report the synthesis of millimeter-sized GeI 2 single crystals, utilized as a broadband photodetector. The material was grown directly from its elements in a large-scale vapor transport method. The resulting freestanding crystals, with a diameter of up to 5 mm, were characterized through structural and optical measurements. Subsequently, a metal−semiconductor− metal broadband photodetector was fabricated. The as-fabricated device exhibited promising performance in photocurrent measurements when subjected to a 460 nm laser with a power density of 3.8 mW cm −2 , including a high responsivity of 21.1 mA W −1 , a relatively fast photoresponse speed (a rise time of 0.16 s and a decay time of 0.5 s), and a commendable specific detectivity of 5.54 × 10 7 Jones at room temperature.