Abstract
Abstract
Thermodynamic analyses for the growth of group-III sesquioxides, including α-Al2O3, β-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 (
Δ
P
III
2
O
3
) 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,
Δ
P
III
2
O
3
decreased with increasing
P
III
o
and/or decreasing input partial pressure of O3 or O. This decrease was caused by the formation of Ga2O or In2O during growth of β-Ga2O3 and c-In2O3. The decrease of
Δ
P
Al
2
O
3
was smaller because the equilibrium constant of α-Al2O3 formation reaction was very large. Ga and In droplets formed at low temperatures (<420 °C), whereas Al droplets were formed at high temperatures (<820 °C), and the order that enabled growth at higher temperatures was c-In2O3 < β-Ga2O3 << α-Al2O3.
Funder
Japan Society for the Promotion of Science
Subject
General Physics and Astronomy,General Engineering