Interface structure and bias dependence of VN/AlN/VN tunnel junction: A semi-empirical calculation

Abstract

Vanadium Nitride based magnetic heterostructures have opened up unprecedented opportunities in the field of spintronics owing to their half metallicity and a high value of spin polarization. In this paper, a tight-binding model of epitaxially grown VN/AlN/VN heterostructure is developed with different types of bonding at the left and right interface. The Slater–Koster tight-binding scheme is used to obtain the on-site and hopping energies of the model by fitting them to bulk DFT band structures. Electron transport across the VN/AlN/VN heterostructure is then studied using the non-equilibrium Green’s function method, which works well within the tight-binding framework. An asymmetry in the interface bonding of the structure was found to produce a resonance peak in the transmission spectra at around 0.5 V. Beyond 0.5 V, the tunnel junction registers a large antiparallel current resulting in a negative tunnel magnetoresistance. Moreover, the presence of a magnetic impurity in the insulating barrier enhances tunneling across the junction resulting in a large current that decreases with the value of intra-atomic Coulomb repulsion, U, at the impurity site.