Abstract
In this paper, phosphorene nanoribbons (PNRs) are theoretically studied using a multiscale simulation flow from the ab initio level to the tight binding (TB) level. The scaling effects of both armchair PNRs (aPNRs) and zigzag PNRs (zPNRs) from material properties to device properties are explored. The much larger effective mass of holes compared to that of electrons in zPNR is responsible for its asymmetric transport. However, in aPNR, not only the effective mass difference but also the non-equal density of state (DOS) distributions near valence band maximum (VBM) and conduction band minimum (CBM) lead to the asymmetric transport. This non-equal distribution phenomenon is caused by energy band degeneracies near the VBM. Based on these two different mechanisms, PNRs’ asymmetric transport characteristics at the device level are explained, and it is shown that this behaviour can be ameliorated well by reducing the ribbon width in an aPNR MOSFET. Calculation results also indicate that aPNR’s effective mass is comparable to that of a graphene nanoribbon (GNR) at the same bandgap; however, aPNR’s band gap variation is more stable and regular than that of GNR, making it a good candidate for use in low-dimensional nano devices.
Highlights
Two-dimensional materials such as monolayer graphene and MoS2 are extensively studied for the development of planar technology
We found that the hole current in armchair phosphorene nanoribbons (PNRs) is larger than the electron current, while in zigzag PNR, the electron current is larger than the hole current, demonstrating the asymmetric transport in PNRs
Simulations reveal that asymmetric transport behaviour exists in both armchair PNRs (aPNRs) and zigzag PNRs (zPNRs) devices
Summary
Two-dimensional materials such as monolayer graphene and MoS2 are extensively studied for the development of planar technology. As a naturally non-zero bandgap material, monolayer MoS2 is regarded as another competitive candidate for use in two-dimensional nano devices[5,6,7,8]. Other researchers used computation theories such as the k · p d and effective mass methods[10,28] In these methods, the key parameters are obtained from large area phosphorene, without considering the edge effect of PNR. Their availability and accuracy in PNR, especially when including the scaling effect, are limited. We introduce a new method for simulation of the material and transport properties of PNR This simulation procedure has been verified for silicon and carbon devices, as reported in our previous works[29,30]. These TB parameters obtained from the Wannier transformation describe PNR’s material properties more precisely than those obtained directly from large area phosphorene
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