Photoconductive multi-layer graphene photodetectors fabricated on etched silicon-on-insulator substratesr**Project supported by the National Key Research and Development Program of China (Grant No. 2016YFB0402404), the High-Tech Research and Development Program of China (Grant Nos. 2013AA031401, 2015AA016902, and 2015AA016904), and the National Natural Science Foundation of China (Grant Nos. 61674136, 61176053, 61274069, and 61435002).

Abstract

Recently, graphene-based photodetectors have been rapidly developed. However, their photoresponsivities are generally low due to the weak optical absorption strength of graphene. In this paper, we fabricate photoconductive multi-layer graphene (MLG) photodetectors on etched silicon-on-insulator substrates. A photoresponsivity exceeding is obtained, which enables most optoelectronic application. In addition, according to the analyses of the high photoresponsivity and long photoresponse time, we conclude that the working mechanism of the device is photoconductive effect. The process of photons conversion into conducting electrons is also described in detail. Finally, according to the distinct difference between the photoresponses at 1550 nm and 808 nm, we estimate that the position of the trapping energy is somewhere between 0.4 eV and 0.76 eV, higher than the Fermi energy of MLG. Our work paves a new way for fabricating the graphene photoconductive photodetectors.