【Epitaxy Papers】Effect of nitrogen annealing treatment on the crystal structure and band alignment of atomic layer deposition deposited β−Ga₂O₃

      Researchers from the Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences have published a dissertation titled "Effect of nitrogen annealing treatment on the crystal structure and band alignment of atomic layer deposition deposited β−Ga₂O₃" in Ceramics International.

Abstract

      In this work, (400)-oriented polycrystalline β-Ga₂O₃ thin films were deposited on sapphire (0001) by atomic layer deposition (ALD) for the first time, followed by annealing at 600–1200 °C in nitrogen (N₂) atmosphere. The effects of annealing temperature on the crystal structure, chemical composition, defect states, and optical properties of the (400)-oriented Ga₂O₃ thin films were comprehensively investigated. Atomic force microscopy (AFM) images indicated that the grain size and roughness gradually increased with the temperature. X-ray diffraction (XRD) patterns showed that the (400) diffraction peak significantly enhanced after annealing, which reached the optimum at 1000 °C. X-ray photoelectron spectroscopy (XPS) patterns illustrated that the annealing treatment reduced the oxygen vacancy (V_O), when annealed reached 800–1000 °C, the nitrogen atoms occupied V_O further reducing the V_O concentration, and the optimum crystallinity was reached under 1000 °C with a lattice oxygen ratio (O_L/(O_L + O_NL)) = 80.52 %). The band gap and energy band alignment were extracted by XPS and UV–vis, after annealing the band gap increased from 4.80 to 5.53, and the VBM changed from 2.5 to 1.97 eV. Density Functional Theory (DFT) simulations further elucidate the energy band shifts induced by V_O changes and nitrogen-filled V_O, demonstrating the mechanism of passivation defects in nitrogen annealing. This study provides an in-depth study and explanation of the mechanism of nitrogen annealing, which provides guidance and reference for further preparation of high-quality Ga₂O₃ thin films and their application in high-performance devices.

DOI：

https://doi.org/10.1016/j.ceramint.2025.04.296