Optical Helicity and Polarization Dependent NIR Negative Photocurrent in the 2D Magnetic Semiconductor CrI₃

Abstract Two‐dimensional magnetic semiconductors provide a fascinating platform for studying magneto‐optoelectronic properties at the atomically thin limit and have potential in developing novel devices. In this paper, the superior negative photoconductivity (NPC) characteristics of graphene‐CrI₃‐graphene van der Waals heterostructure in light detection, such as a broader detection range (650–1250 nm) and faster response time (<0.32 ms), as well as light helicity and polarization sensitivity are reported. Under near‐infrared (NIR) light illumination, the NPC‐related photoresponsivity R and specific detectivity D* are 1.18 A W⁻¹ and 1.26 × 10⁹ Jones, respectively. Under magnetic field conditions, the NPC and positive photoconductivity (PPC) show opposite optical helicity dependence. The photoresponsivity helicity of the NPC‐dominated photocurrent can reach 16.01%. Besides, NPC and PPC show obvious and similar linear polarization dependence, independent of magnetic fields. It is demonstrated that NPC is superior to PPC in some aspects, such as fast detection of red and NIR lights as well as their helicity and polarization, especially in the NIR region. This work explores many unique phenomena of NPC, further revealing the interplay between magnetic and optoelectronic properties in CrI₃, and paves the way for expanding traditional photoelectric detection and optical communication with higher data transmission rates.