Yuichi Oshima, Takayoshi Oshima
We demonstrated rapid homoepitaxial growth on (011) β-Ga2O3 substrates using HCl-based halide vapor phase epitaxy (HVPE), in which GaCl was synthesized by reacting metallic Ga with HCl gas, and examined properties of the resulting layer. These were compared with layers grown using Cl2-based HVPE, where GaCl was produced from Ga and Cl2. The growth rate on (011) substrates, approximately 60% of that on (001), reached ~14 μm/h, which was 5–7 times higher than those previously reported for Cl2-based HVPE. Despite this high rate, no polycrystalline grains, sometimes found in Cl2-based HVPE, were detected. Atomic force microscopy revealed a surface with root-mean-square roughness of 6.5 nm over a 100 × 100 μm2 area. In contrast, Nomarski microscopy revealed the presence of pits (~10 μm in diameter at 3.6 μm thickness) with a density of ~3.7 × 103 cm−2, a feature not reported for Cl2-based HVPE. Cross-sectional transmission electron microscopy confirmed the absence of crystal defects or inclusions at the pit bottom. X-ray diffraction 2θ–ω scans and pole figure measurements confirmed that the epitaxial layers were single crystalline, with rocking-curve FWHM values comparable to or smaller than those of the substrate. Secondary ion mass spectrometry revealed a chlorine concentration of 1.7 × 1015 cm−3, which was significantly lower than 1.1 × 1016 cm−3 measured in the (001) layers. Thus, while the pit issue requires further investigation, HCl-based HVPE enables the rapid growth of low-chlorine (011) β-Ga2O3, offering significant potential for cost reduction in high-performance power devices with thick drift layers.