1 State Key Laboratory for Information Photonics and Optical Communications, School of Electronic Engineering, Beijing University of Posts and Telecommunications, Beijing 100876, China; 2 Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
Abstract Strontium titanate (SrTiO3), which is a crucial perovskite oxide with a direct energy band gap of 3.2 eV, holds great promise for ultraviolet (UV) photodetection. However, the response performance of the conventional SrTiO3-based photodetectors is limited by the large relative dielectric constant of the material, which reduces the internal electric field for electron-hole pair separation to form a current collected by electrodes. Recently, graphene/semiconductor hybrid photodetectors by van-der-Waals heteroepitaxy method demonstrate ultrahigh sensitivity, which is benefit from the interface junction architecture and then prolonged lifetime of photoexcited carriers. Here, a graphene/SrTiO3 interface-based photodetector is demonstrated with an ultrahigh responsivity of 1.2× 106 A/W at the wavelength of 325 nm and ∼ 2.4× 104 A/W at 261 nm. The corresponding response time is in the order of ∼ ms. Compared with graphene/GaN interface junction-based hybrid photodetectors, ∼ 2 orders of magnitude improvement of the ultrahigh responsivity originates from a gain mechanism which correlates with the large work function difference induced long photo-carrier lifetime as well as the low background carrier density. The performance of high responsivity and fast response speed facilitates SrTiO3 material for further efforts seeking practical applications.
(Photodetectors (including infrared and CCD detectors))
Fund: Project supported by the National Key Research and Development Program of China (Grant Nos. 2017YFF0104801 and 2018YFB0406601) and the National Natural Science Foundation of China (Grant Nos. 61804012 and 11721404).
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