High-Performance Photodetectors Based on Graphene/MoS₂ Heterojunction FETs

Abstract

Being an excellent representative of atomically thin 2-D materials, graphene has attracted extensive research attention in the fields of electronic and optoelectronic devices. However, its low-light absorption coefficient, gapless nature, and short carrier lifetime hinder its development in photodetectors. Another atomically thin 2-D semiconducting material molybdenum disulfide (MoS2) has stronger light interaction. Here, we show a high-performance photodetector based on graphene/MoS2 heterojunction field effect transistors (FETs), where the electrodes are fabricated in the middle of two materials. Graphene functions as a conductive material that improves the carrier transmit speed of the device. Meanwhile, MoS2 mainly functions as a light-sensitive material that promotes the generation of photogenerated carriers. The combination of the two materials substantially improves the performance of the photodetector. The photoresponsivity of our device was demonstrated up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${1.5} \times {10} ^{{4}}$ </tex-math></inline-formula> A/W under a 470-nm light-emitting diode (LED) light illumination, which was much higher than that of a reported photodetector based on monolayer graphene or MoS2 (~mA/W). Moreover, the photoresponsivity of the device could be easily tuned by applying buried-gate, back-gate, and source–drain voltage, which has important implications for the application of 2-D material photodetectors in neural network image sensor arrays. Our study established a method for large-scale preparation of high-performance photodetector arrays based on 2-D materials heterojunctions.