Microstructure of bulk GaN layer grown on sapphire substrates with amorphous buffer

The structure of bulk GaN layers grown on (0001) sapphire substrates by vap or-phase epitaxy has been studied by x-ray diffraction and transmission ele ctron microscopy (TEM). It is found that these layers contain grown-in and screw dislocations. The dislocation density decreases away from the interfa ce. The effect of an amorphous buffer layer on the formation of the initial GaN layer and, thus, on the degree of perfection of gallium nitride layers is elucidated. A model of generating grown-in dislocations and the relaxat ion mechanism of misfit stresses are proposed. (C) 2000 MAIK "Nauka/Interpe riodica".