Abnormal Electron Emission in a Vertical Graphene/Hexagonal Boron Nitride van der Waals Heterostructure Driven by a Hot Hole-Induced Auger Process.

Understanding the scattering process of field injection hot carriers is important for modulating their behaviors, which is the key for improving the efficiency of charge transfer and energy conversion in hot carrier devices. In this work, a significant electron thermalization induced by Auger scattering between a field injection hot hole and a native cold electron has been observed in a vertical single layer graphene/hexagonal boron nitride/few layer graphene (Gr/hBN/FLG) device by measuring the vacuum electron emission characteristics. For the first time, it is found that vacuum electron emission can be measured under both directions of bias within the device. Furthermore, electrons can be emitted even when the applied bias energy is smaller than the work function of the Gr cathode. Further analysis of the emission electron kinetic energy indicates that the low turn-on bias results from the emission of energetic electrons that are ∼3 eV higher than the Fermi level. A semiquantitative model based on hot hole-induced Auger electron emission is established to reproduce the results. All of these findings not only expand our understanding of the hot carrier scattering process in graphene but also provide insights into the applications of hot carrier devices.