10 2 cm u2212 2 nitride crystal 101 also preferably has a stacking fault concentration below 10 3 cm u2212 1 10 2 cm u2212 1 10 cm u2212 1 or even below 1 cm u2212 1 nitride crystal 101 also has a symmetric x ray rocking curve full width at half maximum fwhm less than about 300 arc sec 200 arc sec 100 arc sec 50 arc sec 35 arc sec 25 arc sec or even less than about 15 arc sec nitride crystal 101 has a crystallographic radius of curvature greater than 0 1 meter 1 meter 10 meters 100 meters or even greater than 1000 meters in up to three independent or orthogonal directions nitride crystal 101 has regions having a relatively high concentration of threading dislocations separated by regions having a relatively low concentration of threading dislocations the concentration of threading dislocations in the relatively high concentration regions may be greater than about 10 6 cm u2212 2 10 7 cm u2212 2 or even greater than about 10 8 cm u2212 2 the concentration of threading dislocations in the relatively low concentration regions may be less than about 10 6 cm u2212 2 10 5 cm u2212 2 or even less than about 10 4 cm u2212 2 the thickness of nitride crystal 101 is between about 100 microns and about 100 millimeters or even between about 1 millimeter and about 10 millimeters the diameter of the crystal.