A new method was reported for reducing the dislocation density in a GaN epilayer grown on sapphire by metalorganic chemical vapor deposition, by introducing GaN-rich-GaNP/GaN multiple layers during the growth of the GaN layer. It was found that some threading dislocations bend and/or terminate near the multiple layer region, which would suppress the dislocations propagating to the top film surface. The dislocation density in the films consequently decreases to 6 x 108/cm2 in the GaN epilayer with GaNP/GaN multiple layers, which was a decrease of factor 2 with respect to that in a conventionally grown GaN epilayer. It was considered that the ternary GaN-rich GaNP selectively deposits in the regions of those dislocation-induced pits on the as-grown GaN surface, and then influences the propagation properties of the dislocations. This method could be applied to many devices such as laser diodes whose performance was deteriorated by dislocations.

Dislocation Reduction in GaN Layer by Introducing GaN-Rich GaNP Intermediate Layers. M.Tsukihara, Y.Naoi, H.Li, S.Sakai: Japanese Journal of Applied Physics–1, 2003, 42[4A], 1514-6