Dislocation reduction in GaN layer by introducing GaN-rich GaNP intermediate layers

We report a new method of reducing the dislocation density in a GaN epilayer grown on sapphire by metalorganic chemical vapor deposition (MOCVD), by introducing GaN-rich-GaNP/GaN multiple layers (MLs) during the growth of the GaN layer. It is found that some threading dislocations bend and/or terminate near the ML region, which would suppress the dislocations propagating to the top film surface. The dislocation density in the films consequently decreases to 6×108 cm-2 in the GaN epilayer with GaNP/GaN MLs, which is a decrease of factor 2 with respect to that in a conventionally grown GaN epilayer. It is 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 can be applied to many devices such as laser diodes whose performance is deteriorated by dislocations.