Structural and optical properties of GaN crystals grown by the ammonothermal technique

High quality GaN crystals grown by the ammonothermal method are reported. The grown crystals possess excellent structural and optical properties. As confirmed by X-ray diffractions, the crystals have very low overall Bragg peak broadening and particularly low twist variance. X-ray rocking curves indicate the ammonothermal growth is replicating or improving from the seed crystal, with as low as 65 arc-sec FWHM on (002) when using a 1×3 mm2 unslitted X-ray spot size. Room temperature PL indicates the material has almost no yellow-band emission although the yellow emission peak increased after annealing of the sample at 900 °C. The availability of yellow-band free ammonothermal wafers offers a unique opportunity to study the origin of the yellow-band emission in GaN (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)