Investigation of N-polar InGaN growth on misoriented ScAlMgO₄ substrates

We report the growth of N-polar InGaN layers on misoriented ScAlMgO₄ (SAM) substrates with offset of 0.3 to 5.8° toward the m-plane. The surface of N-polar InGaN with small-offset substrates exhibited hexagonal hillocks similar to those commonly observed in N-polar GaN layers. Larger misorientation angles resulted in smoother surfaces of the InGaN layers. In contrast, the crystalline quality of InGaN indicated an opposite trend with significantly improved quality observed at smaller misorientation angles. We obtained an unprecedented crystalline quality of N-polar InGaN using SAM substrates with a 0.5° offset, which exhibited a 000 2 ¯ X-ray rocking curve full width at half maximum value of 223 arcsec. The crystalline quality and surface morphology of InGaN were significantly influenced by the step surface of substrates according to atomic force microscopy observations.