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Large size and low dislocation density bulk gallium nitride (GaN) crystals were successfully grown by original acidic ammonothermal method SCAAT™ (Super Critical Acidic Ammonia Technology). It enabled us to obtain extremely high crystallinity true bulk GaN. In this article, 2-inch size non-polar m-plane GaN and nearly 4-inch size polar c-plane GaN were demonstrated. The dislocation and stacking fault density of m-plane GaN were in the range of 102 to 103 cm-2 and 0 to 5 cm-1, respectively. The full width at half maximum (FWHM) of X-ray rocking curve (XRC) on (10-12) plane was 6.4 arcsec. The dislocation density of c-plane GaN was in the range of 103 to 104 cm-2. The off-angle distribution of nearly 4-inch size c-plane GaN was ±0.006° in the span of 80 mm. The types of dislocations in the c-plane GaN were identified by transmission electron microscope (TEM) observation. Hydride vapor phase epitaxy (HVPE) growth on the SCAA™ c-plane seed was carried out and obtained 2-inch wafer. The crystallinity was comparable to SCAAT™ seed; FWHM of XRC was less than 10 arcsec and off-angle distribution was ±0.017°. more...

SCAATTM has been developed as a novel ammonothermal method which enables to obtain strain free, high quality and large size bulk gallium nitride (GaN) crystals under high pressure and high temperature super-critical ammonia. One of the unique features of this technique is relatively high growth rate of more than a few hundred micrometers per day toward polar and non-polar axis with excellent crystalline quality. The morphology, X-ray rocking curve, etch pit density and electric properties are presented. more...

Ammonothermal crystal growth of gallium nitride (GaN) was realized for the first time using GaN powder as a nutrient with growth rates of about 61 μm per day on both Ga and N faces. The GaN powder was synthesized by ammonolysis of Ga metal in the presence of NH4I. The crystal quality of the as-grown GaN wafers was characterized by scanning electron microscope (SEM), X-ray rocking curve (XRC) and photoluminescence (PL) measurements. We examined the effect of different nutrients, including polycrystalline GaN, Ga metal, and GaN powder, on the acidic ammonothermal crystal growth of GaN using an NH4I-based mineralizer. Our results suggest that growth rate and crystal quality of GaN depend largely on the type of nutrient. Polycrystalline GaN as a nutrient can afford high growth rates of up to 150 and 237 μm per day on Ga and N faces, respectively. Growth rates up of to 33 μm per day were achieved using Ga metal as a nutrient. However, SEM, XRC, and PL measurements of GaN crystals grown using different nutrients indicate that Ga metal and GaN powder nutrients can provide better crystal quality of GaN in terms of surface morphology and crystal uniformity than polycrystalline GaN. more...

An efficient and mild method to synthesize high-purity hexagonal GaN powder using NH4I as a catalyst was developed. The method makes it possible to use Ga metal for ammonothermal crystal growth of GaN at a rate of 20 μm per day, which is comparable to its growth rate using polycrystalline GaN grown by hydride vapor phase epitaxy as a nutrient. more...