Photo of GaN crystal grown on a sapphire substrate by the sublimation technique. The thickness of the crystal is 0.3 mm. The dark area in the center of the crystal is attributed to Ga droplets accumulated at the interface between sapphire and GaN. The appearance of the droplets at the initial stage of growth is related to lowering of V/III ratio over the substrate from the periphery to the center.
© 1998 The Materials Research Society
