Photo‐Driven Semimetal–Semiconductor Field‐Effect Transistors

Abstract Photodetectors that can simultaneously exhibit high gain, fast response, and low dark current are of significant value in modern optoelectronic systems. However, the recently reported photovoltage‐driven phototransistors are encountering certain challenges to meet the above requirement. In this work, a “photo‐driven” semi‐metal–semiconductor field‐effect transistor (photo‐sMESFET), based on graphene/silicon‐on‐insulator hybrid structure, is proposed and demonstrated to realize the synchronous optimization of gain, response speed, and dark current. Taking advantage of the unique semimetal characteristics of graphene, a high‐quality Schottky junction between graphene and silicon is produced, which can greatly deplete the silicon channel and suppress dark current. After illumination, the photovoltage at graphene–silicon interface efficiently shrinks the depletion layer and tremendously enhances the channel conductance. Combined with the high transconductance of the silicon channel, the photo‐sMESFET exhibits a gain of more than 10⁴, a fast response time (τ) of 3 µs, and a low dark current (J_d) of 2.5 µA. Furthermore, the figure of merit, , evaluating the comprehensive performance on photodetectors, is up to 8 × 10⁸ A^1/2 cm s⁻¹, which is superior to the counterparts of graphene‐based photodetectors. The results presented leverage a new detection strategy based on the semimetal–semiconductor photovoltaic effect.