High Quality Bulk Gan Crystal Grown By Acidic Ammonothermal Method

Acidic ammonothermal method is one of the most promising techniques which enable the mass production of large diameter bulk GaN crystal. State-of-the-art high-power light-emitting diodes and laser diodes are usually fabricated on GaN substrates grown by hydride vapor phase epitaxy. However, to realize vertically conducting high-power GaN switching devices, bowing-free large-diameter GaN substrates are essential, because the size of such devices is much larger than that of optical devices. Our group has been studying the characteristics of supercritical NH 3 using ammonium halides as mineralizers, and succeeded in growing GaN. The crystal quality and the growth rate strongly depend on mineralizer species. We have also studied the dependence on temperature and pressure, and found it possible to achieve the growth rate faster than 1000µm/day in the optimum growth condition. Based on these studies and optimization, we have successfully demonstrated high speed bulk GaN growth at the pressure condition at 100MPa.