Theoretical Study on Atomic Structures of Thermally Grown Silicon Oxide/Silicon Interfaces

Temperature-Dependent HfO2/Si Interface Structural Evolution and its Mechanism

In this work, hafnium oxide (HfO₂) thin films are deposited on p-type Si substrates by remote plasma atomic layer deposition on p-type Si at 250 °C, followed by a rapid thermal annealing in nitrogen. Effect of post-annealing temperature on the crystallization of HfO₂ films and HfO₂/Si interfaces is investigated. The crystallization of the HfO₂ films and HfO₂/Si interface is studied by field emission transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and atomic force microscopy. The experimental results show that during annealing, the oxygen diffuse from HfO₂ to Si interface. For annealing temperature below 400 °C, the HfO₂ film and interfacial layer are amorphous, and the latter consists of HfO₂ and silicon dioxide (SiO₂). At annealing temperature of 450-550 °C, the HfO₂ film become multiphase polycrystalline, and a crystalline SiO₂ is found at the interface. Finally, at annealing temperature beyond 550 °C, the HfO₂ film is dominated by single-phase polycrystalline, and the interfacial layer is completely transformed to crystalline SiO₂.

Ultrathin silicon oxynitride layer on GaN for dangling-bond-free GaN/insulator interface

Despite the scientific and technological importance of removing interface dangling bonds, even an ideal model of a dangling-bond-free interface between GaN and an insulator has not been known. The formation of an atomically thin ordered buffer layer between crystalline GaN and amorphous SiO₂ would be a key to synthesize a dangling-bond-free GaN/SiO₂ interface. Here, we predict that a silicon oxynitride (Si₄O₅N₃) layer can epitaxially grow on a GaN(0001) surface without creating dangling bonds at the interface. Our ab initio calculations show that the GaN/Si₄O₅N₃ structure is more stable than silicon-oxide-terminated GaN(0001) surfaces. The electronic properties of the GaN/Si₄O₅N₃ structure can be tuned by modifying the chemical components near the interface. We also propose a possible approach to experimentally synthesize the GaN/Si₄O₅N₃ structure.