Defect-assisted electron tunneling in 2D Van der Waals heterostructures*

Defect-assisted resonant electron tunneling in hexagonal boron nitride (hBN) is demonstrated via electron transport measurements of graphite/hBN/graphite tunnel junctions. This study reveals distinct resonance peaks in the differential conductance (dI/dV) corresponding to native defect states in hBN. We investigate tunneling in devices fabricated from three sources of hBN and see substantial variation in defect density and electronic activity depending on the source and synthesis method. Further, hBN grown with excess carbon in the reaction chamber shows the emergence of sharp features typically associated with tunneling through point defects. These features are stable on sweep up/down and their temperature dependence reveals thermal broadening that allows for the inference of a zero-temperature inhomogeneously broadened linewidth of 9 meV. These results validate this modular platform as a tool for investigating tunneling spectroscopy of atomic defects in 2D materials and given recent interest in these systems as potential qubits, has a significant potential impact for emerging applications in quantum information.