Thermodynamic and experimental study of β-Ga ₂ O ₃ growth by oxide vapor-phase epitaxy using Ga ₂ O and H ₂ O as precursors

Abstract Thermodynamic analysis of β-Ga 2 O 3 growth by oxide vapor-phase epitaxy (OVPE) using Ga 2 O and H 2 O precursors was conducted, supported by preliminary growth experiments. Calculations clarify practical growth windows as functions of temperature, the H 2 mole fraction in the carrier gas, the input VI/III ratio, and the input partial pressure of Ga 2 O (P o Ga2O ) The analysis revealed that sustained β-Ga 2 O 3 growth above 1000 °C requires careful control of the H 2 mole fraction to balance precursor generation and thermodynamically driven etching. Phase diagrams were constructed as functions of temperature, P o Ga2O , and input VI/III ratio, which delineate the growth and etching regimes. β-Ga 2 O 3 was grown on (0001) sapphire substrates, and the experimentally derived driving forces agree well with the thermodynamic predictions. The results demonstrate that β-Ga 2 O 3 growth using Ga 2 O and H 2 O can be effectively controlled based on thermodynamics, offering a chloride-free, safer alternative for power-device-grade drift layers.