A novel dislocation reducing mechanism was successfully introduced into the conventional 2-step metalorganic vapor phase epitaxial growth method of GaN/sapphire wafer by inserting an additional intermediate-temperature GaN buffer between the low-temperature GaN buffer and the main high-temperature GaN layer. During the growth of the intermediate-temperature GaN buffer, high-density islands with faceted slopes were formed. Vertically propagating dislocations from the GaN/sapphire interface were bent at the faceted slopes so as to gather at the island/island boundaries, where dislocation loops were formed efficiently. Due to such an island induced dislocation control mechanism, the dislocation density was reduced markedly from the 109/cm2 range to the mid-108/cm2 range during the growth of the intermediate-temperature GaN buffer. As a result, the GaN/sapphire wafers with low dislocation density of 3 x 108/cm2 were successfully grown by such a 3-step metalorganic vapor phase epitaxial method, whereas high-density dislocations (109/cm2) remained in the final GaN/sapphire wafers grown by the conventional 2-step growth method without dislocation control.

Realization of Low Dislocation GaN/Sapphire Wafers by 3-Step Metalorganic Vapor Phase Epitaxial Growth with Island Induced Dislocation Control. H.Fujikura, K.Iizuka, S.Tanaka: Japanese Journal of Applied Physics-1, 2003, 42[5A], 2767-72