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Comparative study of epitaxial lateral overgrowth on semipolar (11-22) GaN by using stripe and hexagon SiO2 mask patterns

We investigated defect reduction of epitaxial lateral overgrown (ELO) semipolar (11-22) GaN grown on m-plane sapphire substrate by using stripe and hexagon SiO2 patterns. We obtained the fully-coalescent semipolar ELO-GaN templates successfully regardless of pattern shape and size. However, ELO-GaN film grown on hexagonal patterns were more easily coalesced than ELO-GaN grown on stripe patterns during ELO process due to the lateral growths from six directions. Xray rocking curves from ELO-GaN films indicate that ELO-GaN had much better crystal quality than GaN template. However, the effect of the lateral overgrowth on hexagon patterns on crystal quality was limited because the large frictions from the six-directional growth on hexagon pattern resulted in crystallographic tilts. The photoluminescence emissions of donor-bound exciton (D0X) recombination were observed from both samples, but the D0X emission of stripe ELO-GaN film was considerably stronger than that of hexagon ELO-GaN. In addition, the defect-related emissions of stripe ELO-GaN were also weaker, indicating that stripe ELO-GaN has efficiently eliminated the non-radiative centers and suppressed the defects.