Thermodynamic analysis of molecular beam epitaxy of group-III sesquioxides

Thermodynamic analyses for the growth of group-III sesquioxides, including alpha-Al2O3, ss-Ga2O3, and c-In2O3, by both ozone and plasma-assisted MBE were performed. In either case, under O-rich conditions, the driving force for III2O3 (III = Al, Ga, In) growth (Delta P-III2O3) increased with increasing input partial pressure of the group-III metal (P-III(o)), without generation of metal droplets. Conversely, under group-III-metal-rich conditions, Delta(PIII2O3) decreased with increasing P-III(o) and/or decreasing input partial pressure of O-3 or O. This decrease was caused by the formation of Ga2O or In2O during growth of ss-Ga2O3 and c-In2O3. The decrease of Delta P-Al2O3D was smaller because the equilibrium constant of alpha-Al2O3 formation reaction was very large. Ga and In droplets formed at low temperatures (<420 degrees C), whereas Al droplets were formed at high temperatures (<820 degrees C), and the order that enabled growth at higher temperatures was c-In2O3 < ss-Ga2O3 << alpha-Al2O3. (c) 2023 The Japan Society of Applied Physics

Automated summary

Thermodynamic analyses were performed to study the growth of group-III sesquioxides by ozone and plasma-assisted MBE. The driving force for III2O3 growth increased with increasing input partial pressure of the group-III metal under O-rich conditions, but decreased under group-III-metal-rich conditions. This decrease was caused by the formation of Ga2O or In2O during growth. Ga and In droplets formed at low temperatures, while Al droplets were formed at high temperatures, with the growth order being c-In2O3 < ss-Ga2O3 << alpha-Al2O3.