Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8148367 | Journal of Crystal Growth | 2018 | 14 Pages |
Abstract
Recently, we have reported on the use of the titanium-zirconium-molybdenum alloy (TZM) as an autoclave material for acidic ammonothermal growth of bulk GaN using chloride based mineralizers. Here, we discuss the trends of growths with temperatures ranging from 650 to 900â¯Â°C at pressures around 100â¯MPa in a TZM autoclave. The resulting crystal quality as measured by x-ray diffraction appears to be dependent upon growth thickness. Secondary ion mass spectrometry studies of impurities such as O, H, Cl, and Fe show a tendency to decrease with increasing growth thickness, with concentrations ranging from 1018 to 1020 cmâ3 for O and H, and 5â¯Ãâ¯1016 to 5â¯Ãâ¯1018 cmâ3 for Fe. Cl did not have a standard to quantify the concentration. Ti increased in concentration with increasing growth rate with a range of 4â¯Ãâ¯1014-1â¯Ãâ¯1017 cmâ3. C had steady concentrations between 3â¯Ãâ¯1016 and 5â¯Ãâ¯1017 cmâ3 and the Mo concentration was measured in the low 1016 cmâ3 or less. Zr did not have a standard and thus could not be quantified but was near the detection limit in all cases. The instability of the ammonia solvent at high temperatures requires very high pressures for ammonothermal growth above 800â¯Â°C but short-term growth has been demonstrated up to 900â¯Â°C.
Related Topics
Physical Sciences and Engineering
Physics and Astronomy
Condensed Matter Physics
Authors
Thomas F. Malkowski, James S. Speck, Steven P. DenBaars, Shuji Nakamura,