Effect of ammonia pretreatment on crystal quality of N-polar GaN grown on SiC by metalorganic chemical vapor deposition

Highlights: • Effect of ammonia pre-treatment temperature on N-polar GaN growth was reported. • As pre-treatment temperature increased, N-polar GaN quality was improved. • Best N-polar GaN quality was shown at 1350 °C pre-treatment. • Hillock and inversion domain densities were decreased. • Surface roughness decreased, and crystal quality was improved. -- Abstract: In this study, the effect of NH₃ pre-treatment is investigated to obtain high-quality nitrogen-polar GaN grown on a SiC substrate. The GaN/AlN/C-face 4° off-cut SiC structure is successfully grown with pre-treatment temperatures of 1250, 1300, and 1350 °C. The hillock and inversion domain density, surface roughness, and crystal quality of each sample were evaluated. As the temperature increased from 1250 °C to 1350 °C, the overall crystal quality of the N-polar GaN was greatly improved with reduced hillock and inversion domain densities and smoothed surface. The X-ray rocking curve full-width at half maximum of the (00-2) and (10-2) planes were 374 and 420 arcsec, respectively, for the pre-treatment of 1350 °C.