Tunnel spectroscopy of localised electronic states in hexagonal boron nitride

TL;DR

This study uses gated tunnel transistors to analyze localized electronic states in hexagonal boron nitride, revealing their energies, transmission probabilities, and role in electron percolation, with implications for nanophotonics and quantum tech.

Contribution

It provides detailed characterization of localized states in hBN barriers and introduces a three-step electron percolation process, advancing understanding of tunneling in layered materials.

Findings

Identified over 50 localized states within hBN band gap.

Determined energy levels, linewidths, and transmission probabilities.

Demonstrated a three-step electron percolation process.

Abstract

Hexagonal boron nitride (hBN) is a large band gap layered crystal, frequently incorporated in van der Waals (vdW) heterostructures as an insulating or tunnel barrier. Localised states with energies within its band gap can emit visible light, relevant to applications in nanophotonics and quantum information processing. However, they also give rise to conducting channels, which can induce electrical breakdown when a large voltage is applied. Here we use gated tunnel transistors to study resonant electron tunnelling through the localised states in few atomic-layer hBN barriers sandwiched between two monolayer graphene electrodes. The measurements are used to determine the energy, linewidth, tunnelling transmission probability, and depth within the barrier of more than 50 distinct localised states. A three-step process of electron percolation through two spatially separated localised states is also investigated.