Temperature-Driven Rectification Reversal Observed in Graphene/n-Si(100) Junction

The electrical properties of graphene/semiconductor Schottky junctions have conventionally been explained by the thermionic emission of massless 2D Dirac fermions and the modulation of graphene work-function triggered by the applied bias voltage. So far, most experiments have been conducted at temperatures higher than 77 K, resulting in limited insights into the charge carrier transport across the graphene/semiconductor junction at even lower temperatures. In this study, we present an intriguing phenomenon involving the reversal of rectification direction in the graphene/n-Si(100) junction at approximately 17.5 K. This phenomenon cannot be adequately explained by the existing concepts presented in prior reports. We propose that the temperature-driven rectification reversal originates from the Schottky barrier lowering associated with graphene doping, inhomogeneity of interface energy barrier, and asymmetric nature of inter-dimensional carrier injection between 2D graphene and 3D Si substrate. The asymmetry of carrier injection at the graphene/Si junction can be explained by our hypothesis that the ultra-thin graphene layer enables hot electrons to make multiple attempts of carrier injection from graphene layer into Si substrate before they thermally equilibrate within the graphene layer. The Monte Carlo simulation reveals that the carrier injection between graphene layer and Si substrate becomes increasingly asymmetric as temperature goes down, accompanied by a reduction in the inelastic scattering rate within the graphene layer. These findings offer a new concept of asymmetric inter-dimensional carrier injection, paving the way for realizing a novel type of Schottky diode in which the rectification polarity is controlled by temperature.