CRYSTALLOGRAPHIC PROPERTIES OF BULK GAN CRYSTALS GROWN AT HIGH-PRESSURE

Gallium nitride bulk crystals grown at about 15 kbar and 1500 K have b een examined by using the high resolution X-ray diffractometry. An ana lysis of a set of the rocking curves of various Bragg reflections enab led us to estimate a dislocation density. For the crystals of dimensio ns lower than about 1 mm it is lower than 10(-5) cm(-2). For bigger sa mples the crystallographic quality worsens. With an application of the reciprocal lattice mapping we could distinguish between internal stra ins and mosaicity which are both present in these crystals. The result s for the bulk crystals are compared with those for epitaxial layers.