Dielectric Breakdown in Single-Crystal Hexagonal Boron Nitride

We undertake a dielectric breakdown failure analysis of thin hexagonal boron nitride (h-BN) by conduction atomic force microscopy. The breakdown field is 21 MV cm–1 for 3 nm-thick h-BN, and the breakdown voltage statistics follows a tight monomodal Weibull distribution, indicating the material suitability as a gate dielectric. Breakdown effects extend over an area of ∼100 nm diameter and evolve by defect generation in the h-BN, with increasing conductance under repeated stressing; but the breakdown current–voltage (I–V) curves differ from conventional ultrathin SiO2 and HfO2 films. Specifically, there are indications that 2D layering is influencing the breakdown as follows: (i) Fowler–Nordheim fitting of successive I–V curves after stressing often proceeds in discrete monolayer thickness values of ∼0.3 nm, an effect that we propose arises from electrical "shorting" between adjacent layers, and (ii) the Weibull slope decreases as film thickness increases, indicating that the defect generation is not random but occurs preferentially at specific locations.