Influence of initial surface reconstruction on the interface structure of HfO2/GaAs

We show that the bonding structures and electrical properties of the HfO2/GaAs interface can be controlled by a choice of the reconstruction on the initial GaAs surface. Electron-beam evaporation of HfO2 onto the c(4 × 4) surface yielded As-O bonds at the interface, while Ga-O bonds were dominant at the interfaces formed on the (2 × 4) and (4 × 6) surfaces. Influences of the initial surface reconstruction on the interface structure persisted even after annealing at 673 K. Electrical characterization of Ir/HfO2/GaAs capacitors indicated that the interfacial As-O bonds cause weak Fermi level pinning. It was also suggested that the interfaces dominated by the Ga-O bonds have trapping states in the upper half of the GaAs bandgap.