Electronic transport in hexagonal zinc chalcogenide monolayers: 2D anisotropic nanodevices

Abstract

The electronic transport properties of hexagonal ZnX (X = S, Se) monolayers have been studied by density functional theory (DFT) and non-equilibrium Green's function (NEGF) methods. Hexagonal ZnX monolayers have two distinct zinc-blende (ZB) and wurtzite (WZ) structures, each with two different directions (zigzag and armchair directions), thus giving rise to significant anisotropy. The ZnSe/ZB-based nanodevice displays the highest current along the zigzag direction, reaching a maximum value of 1.5 μA. This superiority over armchair direction demonstrates a significant anisotropy. At the same time, the current increases obviously under the control of gate voltage, and the maximum value can reach 3.4 μA. The photocurrent of the devices based on hexagonal ZnX monolayers also shows apparent anisotropy. The photocurrent of the ZnS/ZB-based device along the armchair direction reaches the maximum value of 15.1 a02/photon. The hexagonal ZnX monolayer-based devices achieve great extinction ratio, for instance 752.4 for ZnS/ZB-based device along the armchair direction. The excellent electronic and optoelectronic transport properties make hexagonal ZnX monolayers promising to be utilized as various electronic and optoelectronic devices.