Growth and characterization of n-type Ga2O3 films on sapphire substrates by APMOVPE

• Published in: Journal of crystal growth 2025-01, Vol.650, p.128007, Article 128007
• Main Authors: Ukita, Shun, Tajiri, Takeyoshi, Uchida, Kazuo
• Format: Article
• Language: English
• ISSN: 0022-0248
• DOI: 10.1016/j.jcrysgro.2024.128007

•n-Ga2O3 films were grown on c-plane sapphire by APMOVPE, using TEOS.•Achieving an electron concentration of nearly 1 × 1017 cm−3 by Si doping.•Deposited films were polycrystalline, stable β-phase and metastable κ-phase.•Appropriate growth temperature and Si doping enhanced the optical transmittance. In this study, n-type Ga2O3 thin films were grown on c-plane sapphire substrates by atmospheric pressure metalorganic vapor phase epitaxy using tetraethoxysilane (TEOS) as the silicon (Si) precursor. X-ray diffraction measurements confirmed that the deposited films were polycrystalline, predominantly consisting of the stable β-phase and the metastable κ-phase. Surface and optical characterizations indicated that lower growth temperature and appropriate Si doping reduce the grain size of three-dimensional Ga2O3 islands, thereby enhancing optical transmittance by mitigating surface scattering. Hall effect measurements demonstrated a maximum electron carrier concentration of approximately 1 × 1017 /cm3 at room temperature, while secondary ion mass spectrometry (SIMS) revealed that Si atomic concentrations were exceeding 1 × 1020 /cm3 in all n-type samples indicating low doping efficiency of Si. Carbon (C) impurities were also measured by SIMS with concentrations as the same order or higher than that of Si, implying they may be one of the reasons for the degraded electrical conductivity and originated from incomplete decomposition of the precursors during low temperature growth. From these results, it is crucial to reduce C impurities and enhance surface flatness to improve electrical and optical properties.