High‐Performance Photoresponse in Ferroelectric d1T‐MoTe₂‐Based Vertical Photodetectors

Abstract Photodetectors based on 2D transition‐metal dichalcogenides (TMDs) are actively investigated to find promising structures with competitive photoresponsivity. Here, a ferroelectric TMD‐based vertical photodetector with asymmetric graphene contacts is proposed, which is modulated with a poling field for controlled built‐in potentials. Thus far, no device is reported, which combines the ferroelectricity of a 2D TMD for an ideal built‐in potential with a vertical structure to reduce the channel length. A ferroelectric phase is obtained in 2D molybdenum ditelluride (MoTe₂) by intensive laser irradiation, which transforms the 2H‐MoTe₂ phase to distorted 1T (d1T)‐MoTe₂. The subsequent poling of d1T‐MoTe₂ with −8 V bias results in a photoresponsivity of ≈853 A W^–1 under 532 nm illumination at zero gate voltage, which is nearly ≈4.5 times higher than that of the 2H‐MoTe₂‐based reference. The achieved photoresponsivity is the best value thus far compared to the reported values for 2D MoTe₂‐based UV–vis photodetectors. The origin of these enhancements is discussed in terms of changes in built‐in potential at the junctions with asymmetric graphene layers based on the adjusted band alignments driven by the poling field.