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Schematic depiction of selective area -plane GaN growth on patterned Si(112) substrates. Since growth is initiated on the vertical sidewalls, the threading dislocations propagate along the -axis and not toward the surface.
(a) An angled cross-sectional SEM image of a patterned Si(112) substrate ready for GaN epitaxy, where the vertical sidewall is covered by AlN. The top Si(112) plane and the tilted Si(111) plane are both masked with . (b) Plan-view and (c) angled cross-sectional SEM images of an -GaN sample grown on a patterned Si(112) substrate after a 3 h growth. (d) Enlarged cross-sectional SEM image showing the growth of the m-GaN initiated at the vertical sidewalls.
(a) On-axis XRD scan showing that the GaN has -plane orientation. The Si(112) plane does not have a diffraction peak due to diffraction extinction. The inset shows the off-axis scan results, suggesting that is oriented 180° away from Si(111). (b) XRD rocking curves of -plane after a 3 h growth, rocking toward the GaN -axis and -axis.
Room-temperature PL spectra measured with a He–Cd laser at different excitation densities for 6-nm-thick InGaN DH LED active layers on (a) -GaN on sapphire and (b) -GaN on Si. No blueshift is observed in the emission peak of the -plane sample. The excitation power densities in [(a) and (b)] were 0.05, 0.15, 0.52, 1.0, 2.0, 2.5, and . The inset in (b) shows the IQEs of both samples extracted from the excitation dependence of the PL intensity using a Ti-sapphire laser (370 nm).
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