The dependence of growth temperature for the epitaxial films grown by tri-halide vapor phase epitaxy (THVPE) on the crystal characteristics, such as the surface morphology, the full width at half maximum (FWHM), the threading dislocation density (TDD), the impurity concentration, and the photoluminescence (PL) was investigated. The epitaxial films grown at relatively high growth temperature of 1300-1350 °C showed that the crystal quality, such as FWHM and TDD retained that for the used substrate. The near-band-edge emission for PL for 1300-1350 °C growth showed lager intensities due to low nonradiative recombination center (NRC). Moreover, the epitaxial growth on the supercritical acidic ammonia technology (SCAAT™) substrate was demonstrated. The TDD was as low as 2 × 104 cm-2, which indicated that the epilayer grown by THVPE retained the superior crystal quality of SCAAT™.
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°.