Ultrasensitive photodetectors based on monolayer MoS2

Two-dimensional materials are an emerging class of new materials with a wide range of electrical properties and potential practical applications. Although graphene¹ is the most well-studied two-dimensional material, single layers of other materials, such as insulating BN (ref. 2) and semiconducting MoS₂ (refs 3, 4) or WSe₂ (refs 5, 6), are gaining increasing attention as promising gate insulators and channel materials for field-effect transistors. Because monolayer MoS₂ is a direct-bandgap semiconductor^7,8 due to quantum-mechanical confinement^7,9,10, it could be suitable for applications in optoelectronic devices where the direct bandgap would allow a high absorption coefficient and efficient electron–hole pair generation under photoexcitation. Here, we demonstrate ultrasensitive monolayer MoS₂ phototransistors with improved device mobility and ON current. Our devices show a maximum external photoresponsivity of 880 A W^‑1 at a wavelength of 561 nm and a photoresponse in the 400–680 nm range. With recent developments in large-scale production techniques such as liquid-scale exfoliation^11,12,13 and chemical vapour deposition-like growth^14,15, MoS₂ shows important potential for applications in MoS₂-based integrated optoelectronic circuits, light sensing, biomedical imaging, video recording and spectroscopy.