Origin of Voltage‐Dependent High Ideality Factors in Graphene–Silicon Diodes

Abstract

AbstractUndoubtedly 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 (η = 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.