石墨烯/h-BN/石墨烯三明治结构日盲紫外探测器研究

直接宽带隙六方氮化硼（h-BN）二维原子晶体具有高的光吸收系数、高的介电强度以及良好稳定性等优势，是制作紫外探测器的最佳候选材料。但二维原子晶体厚度有限导致光吸收较弱，同时其电输运性能较差，成为发展h-BN紫外探测器的两个瓶颈因素。本项目中，我们拟采用金属纳米颗粒表面等离激元的近场增强效应提高h-BN二维原子晶体光吸收，从而提高器件的光响应度。另一方面，利用石墨烯/h-BN/石墨烯三明治结构，通过外加栅压或偏压调控石墨烯费米能级，使电子和空穴分别注入到上下两层石墨烯中输运，实现光吸收与载流子输运的空间分离。该思路不仅可克服h-BN导电性不足的问题，还可以避免载流子复合，从而提高器件性能。通过该项目的实施，我们期望探明金属表面等离激元对h-BN光吸收的影响，揭示新型器件中载流子的输运与复合机制，最终实现h-BN紫外探测器的高效光电转化，为发展基于h-BN二维原子晶体的日盲紫外探测器奠定基础。

As one of two-dimensional (2D) atomic crystals, hexagonal boron nitride (h-BN) is considered to be a promising material for fabricating ultraviolet (UV) detectors because of its wide direct band gap, high optical absorption, high dielectric strength, and good thermal stability. The following two issues have to be addressed for fabricating the ultraviolet detector based on 2D h-BN atomic crystals: the weak optical absorption owing to its few-atomic layer thickness and the poor conductivity due to its wide band gap. In the present project, we propose to enhance the light absorption of h-BN, and thus the photoresponsivity of the device, by the use of the field enhancement resulting from the excitation of surface plasmons of metal nanoparticles. On the other hand, to overcome the low conductivity of h-BN, a graphene/h-BN/graphene sandwich structure will be used to fabricate the UV detectors, in which the electron-hole pairs are produced in the h-BN layer after light absorption and subsequently are respectively injected into the top and bottom graphene layers due to the presence of a perpendicular electric field created by the applied gate or bias voltage. Furthermore, the carrier recombination in the devices will be avoided due to the electron-hole separation, which is also favorable for improving device performance. The goal of the present project is revealing the effects of local surface plasmons on the light absorption of h-BN, and elucidating the transport and recombination mechanism of photo-generated carriers, and eventually fabricating the solar-blind UV detectors with the high photoresponsivity. The findings of this project will offer a promising approach toward the fabrication of the solar-blind UV detectors for practical applications.