Crystals were grown from solutions of liquid Ga, alloyed with Mg, under high N pressures. They were highly resistive and of very good structural quality, according to X-ray diffraction measurements. The high quality was also confirmed by selective etching of the N-polar (00•¯1) surface in molten KOH-NaOH eutectic. This revealed etch-pit densities which were as low as a few tens per cm2. Etching of Mg-doped crystals in a hot mixture of H3PO4 and H2SO4 revealed, as well as etch pits corresponding to dislocations, hillocks which were not observed on crystals grown without Mg. The hillocks were often arranged into periodic arrays which corresponded to growth macro-steps on the crystal surface. In order to identify the defects which were responsible for these etching effects, the crystals were studied by means of transmission electron microscopy. These measurements confirmed that the crystals were free from grown-in dislocations, although bands of micro-defects were observed.

Micro-Defects in Nearly Dislocation-Free GaN Doped with Mg during High Pressure Crystallization I.Grzegory, J.A.Kozubowski, J.Borysiuk, J.L.Weyher, M.Bockowski, B.Lucznik, S.Porowski: Physica Status Solidi B, 1999, 126[1], 537-40