Asymmetric Carrier Injection in Inter-Dimensional Graphene/Si Junction

Abstract

An intriguing rectification reversal was observed experimentally in graphene/n-Si(001) Schottky junction at 17.5 K while the junction being cooled down. This phenomenon cannot be explained by any of the carrier transport mechanisms that have been addressed until now. We suggest that this rectification reversal can originate from the asymmetric nature of carrier injection across the inter-dimensional(2D/3D) interface of graphene/n-Si(001) junction. The finite electronic thickness of graphene and nonzero out-of-plane group velocity can naturally permit the vertical oscillatory motion of hot electrons within the graphene layer before the occurrence of inelastic scattering, causing the enhancement of forward carrier injection efficiency while the reverse counterpart is suppressed. For figuring out what drives the rectification reversal, we performed the numerical calculations that adopted the Monte Carlo wave function approach and the simplified 1D piecewise constant potential model to harness the dissipation of hot electron energy in graphene and quantum-mechanical description of electron motion. The calculations reveal that the forward carrier injection efficiency can drastically drop as the inelastic scattering rate is reduced in the graphene layer. This large decrease of forward carrier injection efficiency makes the forward current become much smaller than the reverse current, leading to the rectification reversal eventually. We also provide a proof-of-concept demonstration for the sensor-less temperature-triggered auto-control of cryogenic system based on this anomalous rectification behavior of graphene/n-Si(001) junction. Our findings can initiate active research activities for the asymmetric carrier injection in vertical 2D/3D Schottky junctions.