Light helicity detector based on 2D magnetic semiconductor CrI.

Two-dimensional magnetic semiconductors provide a platform for studying physical phenomena at atomically thin limit, and promise magneto-optoelectronic devices application. Here, we report light helicity detectors based on graphene-CrI-graphene vdW heterostructures. We investigate the circularly polarized light excited current and reflective magnetic circular dichroism (RMCD) under various magnetic fields in both monolayer and multilayer CrI devices. The devices exhibit clear helicity-selective photoresponse behavior determined by the magnetic state of CrI. We also find abnormal negative photocurrents at higher bias in both monolayer and multilayer CrI. A possible explanation is proposed for this phenomenon. Our work reveals the interplay between magnetic and optoelectronic properties in CrI and paves the way to developing spin-optoelectronic devices.