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.