The electronic properties of the interface structure between ZnO and amorphous HfO2

We investigate the atomic structure of the interface between crystalline ZnO and amorphous HfO2 (a-HfO2) and the electronic properties of oxygen vacancy (VO) near the interface through first-principles density-functional calculations. From the band alignment of ZnO/a-HfO2 interfaces, the conduction band offset is estimated to be 2.14–2.39 eV, while the potential barrier for hole conduction is nearly zero. The defect level of VO is higher in gate oxide than in ZnO. As VO behaves as a charge trap center in gate oxide, this defect can cause threshold voltage instability, while it does not in the ZnO region.