Togashi Rie, Kisanuki Yumi, Goto Ken, Murakami Hisashi, Kuramata Akito, Yamakoshi Shigenobu, Monemar Bo, Koukitu Akinori, Kumagai Yoshinao
Jpn. J. Appl. Phys. 55(12) 1202BE 2016年11月14日
The thermal and chemical stabilities of group-III sesquioxides (Al<inf>2</inf>O<inf>3</inf>, Ga<inf>2</inf>O<inf>3</inf>, and In<inf>2</inf>O<inf>3</inf>) were comparatively investigated at an atmospheric pressure at heat treatment temperatures ranging from 250 to 1450 °C in a flow of either N<inf>2</inf>or H<inf>2</inf>. In a flow of N<inf>2</inf>, the thermal decomposition of α-Al<inf>2</inf>O<inf>3</inf>was not observed at the temperatures investigated, while the decompositions of β-Ga<inf>2</inf>O<inf>3</inf>and c-In<inf>2</inf>O<inf>3</inf>occurred above 1150 and 1000 °C, respectively, with no generation of group-III metal droplets on the surfaces. In contrast, the chemical reactions of α-Al<inf>2</inf>O<inf>3</inf>, β-Ga<inf>2</inf>O<inf>3</inf>, and c-In<inf>2</inf>O<inf>3</inf>began at low temperatures of 1150, 550, and 300 °C in a flow of H<inf>2</inf>. Thus, the presence of H<inf>2</inf>in the gas flow significantly promotes the decomposition of group-III sesquioxides. The order of thermal and chemical stabilities (α-Al<inf>2</inf>O<inf>3</inf>≫ β-Ga<inf>2</inf>O<inf>3</inf>> c-In<inf>2</inf>O<inf>3</inf>) obtained experimentally was verified by thermodynamic analysis, which also clarified dominant decomposition reactions of group-III sesquioxides.