A {20-21} GaN layer was grown from a c-plane-like sapphire sidewall of a {22-43} patterned sapphire substrate according to the epitaxial relationship between c-GaN and c-sapphire despite {20-21} GaN is not growing on {22-43} sapphire. The as-grown {20-21} GaN layer had an m- and {10-11} facet structure. To improve the {20-21} GaN layer, a wide-terrace was attempted. The defects in the GaN layer were clustered on the m-facets, resulting in a dislocation density of less than 5.6 × 105/cm2 on the {10-11} facets. The {20-21} GaN layer had an excellent photoluminescence spectrum indicating a small number of defects.

Nonpolar and semipolar GaN layers can be selectively grown from sapphire sidewalls of maskless patterned sapphire substrates (PSSs) by selective-area growth using a low-temperature (LT) GaN buffer layer. Various PSSs, such as a-PSS for m-GaN, r-PSS for (1122) GaN, c-PSS for m-GaN, and m-PSS for a-GaN, were prepared to investigate the growth mechanisms. It was revealed that the growth windows of various PSSs to achieve nonpolar or semipolar GaN grown from only the sapphire sidewall by changing the growth conditions are different. To determine the cause of selective-area growth in each PSS, GaN nucleation after annealing of the LT-GaN buffer layer was investigated by scanning electron microscopy, atomic force microscopy and X-ray diffraction analysis. Consequently, GaN was predominantly grown on a region with higher quality and better crystallo-ordered c-oriented GaN nucleation. When such nucleation of GaN occurs on the sapphire sidewall, it proceeds to grow selectively from the sapphire sidewall, and nonpolar or semipolar GaN can be obtained using maskless PSS.

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