The regulation of the withstand voltage performance of ZnO/GaN vertical heterostructures using external electric field and vacancy defects

Abstract

The band gap of the heterostructure determines the withstand voltage. It is very important to regulate the band gap of heterojunctions and to investigate their electrical properties by applying external electric field. Based on density functional theory (DFT), ZnO/GaN vertical heterostructures with two stacking configurations (AB/BA and AB/AB, named H1 and H2, respectively) are constructed. The external electric field and vacancy defects of Zn, Ga, O and N atoms (VZn, VGa, VO and VN) are applied to analyze the electrical properties. The band gap can be tuned from 2.07 eV to 0 eV in H1 and 1.53 eV–0 eV in H2. As the electric field increases, H1 has stronger withstand voltage (−0.84–0.56 V/Å) than H2 (−0.26–0.26 V/Å). In addition, the structures deform obviously with the effect of vacancy defects, but remain stable. The presence of VGa and VN enables H1 and H2 to exhibits metal conductivity and VO change the band types of H1 and H2 from direct to indirect. The results of charge density difference (CDD) prove that a zero potential region and a weak electric field occur at the position of VZn and VO, respectively. Likewise, the external electric field is applied to the defective heterostructures. The bandgap also exhibits strong tunability, and the heterostructure with VO has the largest electric field modulation width. The above results indicate that ZnO/GaN exhibits excellent electrical properties with the influence of VO, which represents potential applications in electronic devices.