MICROSTRUCTURES OF GAN FILMS GROWN BY LOW-PRESSURE METALORGANIC VAPOR-PHASE EPITAXY ON (01(1)OVER-BAR2) SAPPHIRE SUBSTRATES

Microstructures of GaN films grown by low pressure metalorganic vapor- phase epitaxy on (0 1 (1) over bar 2) sapphire substrates were investi gated using transmission electron microscopy. The crystallographic str ucture of the GaN buffer layer grown at 550 degrees C was uniquely hex agonal. Grain boundaries and stacking faults in the as-grown buffer la yer are much less than those in the buffer layer grown on (0 0 0 1) sa pphire substrates. Defects in the as-grown epitaxial layers are predom inantly edge type dislocations with Burgers vector b = 1/3 [1 (1) over bar 0 0]. No screw dislocations or domain boundaries in the epilayer were observed in the as-grown samples. (C) 1998 Elsevier Science B.V. All rights reserved.