High-quality GaN crystals grown from double-polarity hydride vapor phase epitaxy and single-polarization regrowth

In this study, high-quality GaN crystals with low-dislocation density were grown with hydride vapor phase epitaxy (HVPE) followed by polishing and selective area growth. By optimizing the conditions of growth temperature and the ratio of Ga to N, stable double-polarity facet growth on a sapphire substrate was achieved, with dislocation density of the order of 104 cm−2. Dislocations were eliminated into the N-polar regions of the crystal to produce a GaN substrate with single-polarity Ga. After chemical-mechanical polishing (CMP) of GaN with double-polarity solutions of Ga and N, a SiO2 mask was deposited on the N-polar region, and GaN was regrown using HVPE. The resulting GaN substrate grown on the CMP-GaN template had a very flat surface with only single-polarity Ga.