Two-dimensional perovskite oxide as a photoactive high-κ gate dielectric

High dielectric constant (high-κ) gate dielectrics compatible with two-dimensional (2D) semiconductors are essential for scaled optoelectronic devices. However, conventional three-dimensional dielectrics are difficult to integrate with 2D materials with dangling-bond-free surfaces. Here we show that the 2D perovskite oxide Sr₂Nb₃O₁₀, prepared by a top-down approach, can be integrated with various 2D channel materials. The high dielectric constant (24.6) and moderate bandgap of Sr₂Nb₃O₁₀ allow it to be used as a photoactive high-κ dielectric for phototransistors with various 2D channel materials, including graphene, molybdenum disulfide, tungsten disulfide and tungsten diselenide. Molybdenum disulfide transistors exhibit an on/off ratio of 10⁶ with a supply voltage of 2 V and a subthreshold swing of 88 mV dec⁻¹. Tungsten disulfide phototransistors exhibit a photocurrent-to-dark-current ratio of ~10⁶ and ultraviolet (UV) responsivity of 5.5 × 10³A W⁻¹ under visible or UV light illumination, due to the combined effect of gate control and charge transfer from the photoactive gate dielectric. We also show that the phototransistors with the photoactive dielectric can offer UV–visible dual-band photodetection, where UV and visible light illumination are distinguished at separate terminals.