Sensitive Sub‐THz Photodetection in Twisted Graphene with Broad Spectral Response

Abstract The exploitation of photo‐induced hot‐electron effect in graphene has enabled the advancement of ultrafast photodetectors across the visible to sub‐terahertz spectrum. However, the inherent challenges of graphene, including its zero‐bandgap, linear dispersion, and atomic‐scale thickness, impede the device's photo‐electrical conversion efficiency, resulting in a relatively moderate responsivity. Here, monolayer‐bilayer graphene into a moiré superlattice is stacked to generate gate‐tunable bandgaps and significantly modify the band structure, aiming to enhance the device's performance for sensitive broadband photodetection. The dual‐gate twisted monolayer‐bilayer graphene (TMBG) transistor exhibits consistent response patterns across the entire spectral range, with the response mechanisms identified as the photothermoelectric effect, observed without a bias voltage, and the bolometric effect, activated by applying bias. At a sub‐terahertz frequency of 0.3 THz, the transistor demonstrates exceptional performance at a low temperature of 4.5 K, with an optimized external responsivity of 16.9 A W ⁻¹ and a noise equivalent power of 27 fW/Hz ^1/2 and the operational temperature range can be extended up to room temperature. These findings highlight moiré graphene as a promising platform for the development of high‐performance ultra‐broadband detectors, particularly in the sub‐terahertz domain.