【International Papers】RF magnetron sputtering of Ga₂O₃ thin films: Analysis of oxygen flow rate impact on stoichiometry, structural, optical characteristics, and energy band alignments

      Researchers from the Department of Electronics and Communication Engineering, NIT Meghalaya have published a dissertation titled " RF magnetron sputtering of Ga₂O₃ thin films: Analysis of oxygen flow rate impact on stoichiometry, structural, optical characteristics, and energy band alignments" in Materials Science in Semiconductor Processing.

Abstract

      This study employed RF magnetron sputtering with a ceramic stoichiometric Gallium oxide  （Ga₂O₃）target to deposit thin films on c-sapphire substrates, investigating the impact of varying O₂ flow rates on the stoichiometry, structural properties, optical characteristics, and band alignment of the β- Ga₂O₃ films. A significant issue is the preferential sputtering of Ga from the Ga₂O₃ target, which can lead to a deviation from the desired stoichiometry in the deposited films. To address this issue, an effective solution is an appropriate amount of O₂ into the Ar process gas at 400 °C that is utilized during the deposition method. In this case, the X-ray diffraction (XRD) analysis demonstrated that the deposited thin films have a uniform and well-defined single crystalline structure and display a strong (-401) orientation.β-Ga₂O₃ thin films exhibit high transmittance in the visible region and possess a wide band gap, as determined by UV–Visible spectroscopy. The sample deposited with a flow rate of 3 sccm O₂ displayed the desired single-crystalline structure. This result also demonstrated that excessive oxygen impacts the crystallization of the thin film, as verified through X-ray diffraction (XRD) analysis. Furthermore, we explain how oxygen flow rates affect the alignment of the bands in β-Ga₂O₃/Al₂O₃ heterojunctions as measured by XPS and UPS analysis, which has not yet been reported. The results of our study reveal that O₂ flow rates of 3 sccm, 5 sccm, and 10 sccm increased valence band offset (VBO) by 28.5%, 8.1%, and 10.2% respectively, compared to 0 sccm, impacting vertical devices.

Paper Link：https://doi.org/10.1016/j.mssp.2023.107937