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

Abstract

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.