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.