Transparent, low dark current, fast response ultraviolet and short-wavelength blue photons photodetector based on Graphene/SrTiO3 single crystal

Abstract

Ultraviolet light and short-wavelength blue photons (UV-SWB) can cause damage to the human body under excessive exposure. Strontium titanate (SrTiO₃), which is a crucial perovskite oxide with a direct energy band gap of ∼3.2 eV, has great potential for UV-SWB photodetection. In this work, UV-SWB photodetector with high transparency based on Graphene/SrTiO₃ heterojunction was fabricated by graphene transfer method. The Graphene/SrTiO₃ photodetector exhibits an ultra-low dark current of 6 pA at a 30 V bias. The response spectrum of the Graphene/SrTiO₃ photodetector was 220–410 nm, covering the UV-SWB band. Under 385 nm light irradiation, the photodetector exhibits a response of 3.4 mA/W, a detectivity of 1.5 × 10¹⁰ Jones, a response time of 186 ms, and a light-to-dark current ratio of 10³ magnitude at a 30 V bias. In addition, the transmittance of the photodetector in the visible light band reaches 80 %, which has excellent visualization performance. The excellent performance of Graphene/SrTiO₃ photodetector is attributed to the high crystal quality of SrTiO₃ wafer and the van der Waals interface constructed by Graphene/SrTiO₃ reduces the bulk defect density and interfacial state density, which could be beneficial the separation and transport of photogenerated carriers in the active layer and heterojunction. This study has important reference value for the design and manufacture of UV-SWB photodetectors.