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

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.