An investigation was made of GaN buffer layers which had been grown, by low-pressure metalorganic vapor phase epitaxy, onto (00•1) sapphire substrates. As well as forming misfit dislocations, mismatch-induced stresses could also be relaxed by forming stacking faults and micro-twin boundaries parallel to (11¯1) of GaN; near to the GaN/sapphire interface in cubic GaN buffer layers. It was found that, in the case of the latter layers, there existed a critical thickness within which the stacking faults and/or micro-twin boundaries parallel to (11¯1) of GaN could be formed. This critical value was equal to 50nm.

Occurrence of Cubic GaN and Strain Relaxation in GaN Buffer Layers Grown by Low-Pressure Metalorganic Vapor Phase Epitaxy on (00•1) Sapphire Substrates. L.Cheng, K.Zhou, Z.Zhang, G.Zhang, Z.Yang, Y.Tong: Applied Physics Letters, 1999, 74[5], 661-3