Rapid growth of a pit-free (011) β-Ga2O3 homoepitaxial layer with very low residual Si and Cl concentrations by HCl-based halide vapor phase epitaxy

We report the rapid growth of pit-free (011) β-Ga2O3 homoepitaxial layers with very low residual [Si] and [Cl] by HCl-based halide vapor phase epitaxy (HCl-HVPE) in which GaCl was generated from Ga and HCl. Along with the GaCl and O2 growth precursors, additional HCl was introduced directly into the growth zone to suppress parasitic gas-phase reactions. The effects of O2 and additional HCl partial pressures on residual impurity concentrations were systematically investigated. The [Si] decreased sharply with increasing O2 partial pressure before reaching saturation, whereas it increased monotonically with additional HCl partial pressure and fell below the secondary ion mass spectrometry detection limit (1 × 1015 cm−3) in the absence of additional HCl. Thermodynamic analysis of SiO2 etching by H2 and HCl qualitatively reproduced these trends and suggested that residual Si originates predominantly from HCl-induced etching of quartz components in the source zone in the reactor. Even without additional HCl, increasing the GaCl supply enabled a growth rate of 13 μm/h, comparable to that previously achieved with additional HCl, while maintaining [Si] below the detection limit and [Cl] below 2 × 1015 cm−3, without particle-induced surface degradation. Furthermore, no pit formation was observed in the absence of additional HCl, and the pits were found to originate from substrate pre-etching by additional HCl before growth. These findings demonstrate that HCl-HVPE enables rapid homoepitaxy of pit-free (011) β-Ga2O3 layers with very low residual impurity concentrations, offering a promising route toward cost-effective vertical β-Ga2O3 power devices. This study identified the origins of residual Si contamination and pit formation in HCl-HVPE and demonstrates rapid growth of pit-free (011) β-Ga2O3 homoepitaxial layers with very low residual donor concentrations.