Transmission electron microscopy characterization of HfO2/GaAs(001) heterostructures grown by molecular beam epitaxy

Transmission electron microscopy structural characterization of HfO2/GaAs(001) heterostructures grown by molecular beam epitaxy with a film thickness of ∝5 nm was conducted. The study indicates that the room-temperature as-grown films are amorphous and the films crystallize into the monoclinic phase upon in situ post annealing at 540 C in the growth chamber. Both types of films show an atomically sharp interface with GaAs(001) substrates. The crystalline monoclinic HfO2 films exhibit c-oriented epitaxy on the substrate and consist of 90 domains. The formation of 90 domains in the heterostructures, the details of the domain-wall configurations, and the possible impact of the walls and the frequently observed anti-phase boundaries in the films on electrical properties of the heterostructures are discussed. (orig.)