Growth of single-domain (-310) β-Ga 2 O 3 on off-angled sapphire substrates by HVPE

Abstract We demonstrate the heteroepitaxial growth of single-domain (-310)-oriented β-Ga 2 O 3 films on 7° off-angled c-plane sapphire substrates by halide vapor phase epitaxy (HVPE). The influence of HCl flow rate on surface morphology, growth rate, and crystalline quality was systematically investigated. Combined SEM and AFM observations reveal a morphological evolution from island-like growth regions at low HCl flow rates to a relatively uniform, step-flow-like morphology at 65 sccm, followed by pronounced ridge formation and crystallographic faceting at higher flow rates. The maximum growth rate of 13.6 μm h -1 and the minimum (-310) X-ray rocking-curve full width at half maximum of 0.239° are achieved at 75 sccm. X-ray diffraction and asymmetric φ-scan measurements, complemented by cross-sectional transmission electron microscopy and selected-area electron diffraction, confirm phase-pure, single-domain (-310) β-Ga 2 O 3 epitaxy. The observed morphological evolution is qualitatively interpreted in terms of the coupled effects of GaCl precursor supply, effective O/Ga ratio, surface migration and incorporation, and possible gas-phase reactions and selective etching. These findings provide useful guidance for controlling the morphology and crystalline quality of high-rate, single-domain β-Ga 2 O 3 heteroepitaxy on off-angle sapphire substrates.