Enhancing the photoelectrical performance of graphene/4H-SiC/graphene detector by tuning a Schottky barrier by bias
Cunzhi Sun, Xiufang Chen, Rongdun Hong, Xiaomeng Li, Xiangang Xu, Xiaping Chen, Jiafa Cai, Xueao Zhang, Weiwei Cai, Zhengyun Wu, Feng Zhang
Abstract
Graphene/4H-SiC/graphene photodetectors, as well as graphene/4H-SiC heterojunctions, have been fabricated and characterized by utilizing a heating decomposition method. High-quality graphene has been grown on an n− doped 4H-SiC substrate along with a 900 °C hydrogenation process. Temperature-dependent current–voltage characteristics of the graphene/4H-SiC heterojunction have been measured to obtain the Schottky barrier height. The bias-dependent Schottky barrier height (varying from 0.43 eV to 0.41 eV) was found and could result mainly from the electrical doping and Fermi level shifting in graphene. With the increase in the bias, the unsaturated dark current of graphene/4H-SiC/graphene photodetectors indicated the electron diffusion at the graphene/4H-SiC heterojunction. The increased responsivity peaks come from the absorption of the graphene layer in the UV range and the long lifetime of photo-induced thermal electronic carriers being contributed to the bandgap shrinking of graphene and reduction of the Schottky barrier height. The photodetectors biased at 6 V showed a responsivity of 40 A/W, an external quantum efficiency of 1.38 × 104%, and a detectivity of 9 × 1011 Jones, which are larger than those of previously reported similar devices based on graphene/SiO2 or graphene/SiC.