Non‐Saturated Performance Scaling of Graphene Bilayer Sub‐Terahertz Detectors at Large Induced Bandgap

Abstract Electrically induced p − n junctions in graphene bilayer have shown superior performance for detection of sub‐terahertz radiation at cryogenic temperatures, especially upon electrical induction of the bandgap E _g . Still, the upper limits of responsivity and noise equivalent power (NEP) at very large E _g remained unknown. Here, the cryogenic performance of graphene bilayer detectors at f = 0.13 THz is studied by inducing gaps up to E _g ≈ 90 meV, a value close to the limits observed in recent transport experiments. High value of the gap is achieved by using high‐κ bottom hafnium dioxide gate dielectric. The voltage responsivity, current responsivity, and NEP optimized with respect to doping do not demonstrate saturation with gap induction up to its maximum values. The NEP demonstrates an order‐of‐magnitude drop from ≈400 fWHz ^−1/2 in the gapless state to ≈20 fWHz ^−1/2 at the largest gap. At largest induced bandgaps, plasmonic oscillations of responsivity become visible and important for optimization of sub‐THz response.