Band-To-Band Tunneling In A Two Dimension Mono-Layer Black Phosphorus

In this paper, the band-to-band tunneling of a two dimension mono-layer black phosphorus is investigated by using atomistic ab initio method. The results are estimated reasonably by comparing with the results of Wentzen-Krammel-Brillouin (WKB) approximations.Mono-layer black phosphorus (MLBP) as a direct band gap semiconductor structure has applied on field effect transistors. We calculate the transmission coefficient of Zener tunneling in MLBP by use of ab initio method for several central length L. We study the band to band tunneling along x and y direction respectively. It can be found that Zener tunneling along y direction is almost inhibited, which prove the anisotropy of this kind of materials. As we all know, the band gap value is lower than the experimental value when one calculate the band structure by using a local density approximation based on density functional theory. For estimating the difference, we use WKB method to recalculate the transmission coefficients and current densities by considering different band gap. The results are compared with that obtained by ab initio method. In the small V region, the WKB transmission coefficients are larger than the ab initio result, while for large V, the situation is opposite. The reason is that the single band effective mass model ignores the atomic feature difference between the light hole state and conduction band state. Such difference can reduce the coupling between these two states, hence reduces the tunneling current in the ab initio result. Additionally, we can conclude that the current densities are over estimated within 1 order of magnitude due to error of band gap.