Realization of low dislocation GaN/sapphire wafers by 3-step metalorganic vapor phase epitaxial growth with island induced dislocation control

A novel dislocation reducing mechanism was successfully introduced into the conventional 2-step metalorganic vapor phase epitaxial (MOVPE) growth method of GaN/sapphire wafer by inserting an additional intermediate-temperature (IT)-GaN buffer between the low-temperature (LT)-GaN buffer and the main high-temperature (HT)-GaN layer. During the growth of the IT-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 cm^-2 range to the mid-10⁸ cm^-2 range during the growth of the IT-GaN buffer. As a result, the GaN/sapphire wafers with low dislocation density of 3 × 10⁸ cm^-2 were successfully grown by such a 3-step MOVPE method, whereas high-density dislocations (1 × 10⁹ cm^-2) remained in the final GaN/sapphire wafers grown by the conventional 2-step growth method without dislocation control.