Electronic, transport and optical properties of ZnO/GaN heterostructures: first-principles study

Abstract

The electronic, transport and optical properties of the trilayer of ZnO and GaN heterostructures are investigated using density functional study to understand its role in optoelectronic devices. For layered systems, Zn over N and Ga over O stacking arrangement of ZnO over GaN is most favorable. The calculated formation energies reflect the energetically favorable condition of ZnO/GaN heterostructures. The GaN/ZnO/GaN is a more energetically favorable stacking arrangement as compared to ZnO/GaN/ZnO. The band gap of trilayer systems decreases as compared to that of bilayer and monolayer. The ZnO/GaN bilayer and ZnO/GaN/ZnO trilayer show direct band gap characteristics with the value of 1.71 and 1.61 eV, respectively. The GaN/ZnO/GaN shows an indirect band gap of 1.47 eV. The higher recombination rate of ZnO/GaN/ZnO is useful to develop a base for optical emission devices. The transport calculations show that, the magnitude of current flowing through the system increases with the layers of heterosystems and specifically higher for GaN/ZnO/GaN heterostructure. The enhanced channel conductance and higher mobility of GaN/ZnO/GaN heterostructure are crucial for the development of high mobility transistors. The improved absorption energy and dielectric properties are observed for trilayer systems as compared to that of the bilayer and monolayer and may be useful for optical devices. The higher optical efficiency is observed for GaN/ZnO/GaN as compared to ZnO/GaN/ZnO heterostructure system and opens up a way toward optical waveguides and reflectors.