Chemical reaction mechanism between trimethylgallium and oxygen for β-gallium oxide growth: Thermodynamic and experimental studies

Abstract

The metalorganic chemical vapor deposition (MOCVD) dynamics of beta-gallium oxide (β-Ga2O3) growth using trimethylgallium (TMGa) and oxygen as precursors were investigated through both theoretical thermodynamic analysis and experimental validation in a horizontal low-pressure hot-wall reactor. Thermodynamic analysis revealed that high-purity β-Ga2O3 can be grown through the complete combustion of TMG-derived gallium and hydrocarbons. Furthermore, the complete combustion of intentionally supplied hydrogen into the growth system also prevents the degradation of β-Ga2O3 growth. Therefore, a high input VI/III ratio that ensures full combustion of gaseous species in the growth system is preferred for β-Ga2O3 MOCVD. The growth experiments were performed on 2-in. sapphire substrates under an input VI/III ratio of 250. β-Ga2O3 growth was confirmed at growth temperatures between 740 and 950 °C, with the growth rate decreasing from 0.7 to 0.5 μm/h as temperature increased. Thermodynamic analysis successfully reproduced this growth behavior under the effective VI/III ratio of 6.5. The results demonstrate that β-Ga2O3 MOCVD occurred under thermal equilibrium conditions and was thermodynamically controllable.