▎ 摘　　要

Undoubtedly graphene-silicon (GS) heterostructure devices will play significant roles as future rectifiers, potential barrier modulators, photodetectors, photovoltaic devices, biochemical sensors, and so on. However, typical GS devices suffer from unusually wide-range voltage-dependent high ideality factors (eta = 1.1-33.5). To overcome this hurdle, the origin of this wide-range voltage-dependent ideality factor should first be identified but this has not yet been fully studied. This study focuses on identifying the origin using impedance spectroscopy in conjunction with current-voltage, Raman, and X-ray photoemission spectroscopy. The impedance spectra are analyzed with an equivalent distributed circuit model that accounts for the voltage-dependent resistance and capacitance of graphene, the graphene-metal contact, the silicon interface states, and the nonequilibrium behavior in GS junction. This study clearly shows that the voltage-dependent resistance and capacitance of interface states, graphene, and graphene-metal contact are responsible for the wide-range voltage-dependent high ideality factors. This study provides a potential method to overcome the drawbacks of GS devices.