Correlation between the response performance of epitaxial graphene/SiC UV-photodetectors and the number of carriers in graphene

Abstract

Metal-Graphene-Metal (MGM) UV photodetectors have been fabricated by using an Epitaxial Graphene (EG)/SiC junction on a semi-insulating 4H–SiC. The migration of carriers in the EG/SiC photodetectors under 365 nm light irradiation is clarified by introducing a top gate electrode. Besides, it is found that the response performance of EG/SiC photodetectors is affected by the geometric parameters of the graphene channel. When the graphene channel of the detector is reduced from multi-layer to single-layer and its aspect ratio (AR) is increased from 15 to 100, the detector shows a faster response under illumination that its rise time (tr) is reduced from about 20 s to 5 m s, and its decay time (td) reduced from far more than 20 s to 15 m s at a bias of 10 V. At the same time, the responsivity of the detector has been increased to 189.7 mA/V, its External Quantum Efficiency (EQE) has been increased to 66.6 % and its response signal becomes more stable. After systematic analysis, the geometric parameters of the graphene channel are proved to determine the number of carriers in it, the correlation between the response performance of EG/SiC photodetectors and the number of carriers in graphene is found out.