Ammonothermal growth of 2 inch long GaN single crystals using an acidic NH4F mineralizer in a Ag-lined autoclave

Seeded ammonothermal growths of a few-mm-thick GaN crystals on a 2 inch diameter c-plane and a 45 mm long m-plane GaN wafers were carried out by using an NH4F mineralizer in a 60 mm diameter Ag-lined autoclave. As a result of dynamic control of the temperature profile, low dislocation density and nearly bowing-free m-plane GaN was grown: i.e. the full-width at half-maximum values for the X-ray rocking curves of the 10 1 ¯ 0 and 10 1 ¯ 2 reflections were smaller than 28 arcsec and the radius of curvature was estimated to be 1460 m. In addition, its low temperature photoluminescence spectrum exhibited free and neutral donor-bound exciton emission peaks.