Effect of annealing temperature on the optical properties of a bulk GaN substrate

Variation of optical properties in a bulk GaN substrate have experimentally investigated with respect to different annealing conditions of 700 - 1,000 ℃. As-annealed GaN was characterized by scanning electron microscopy, photoluminescence, and Raman spectroscopy. The experimental results demonstrated that the crystallinity and internal residual compressive stress of GaN are most effectively improved when heat-treated at 900 oC for three hours. The optical characteristics were also improved by enhancing the quality of the GaN substrate by decreasing both the defect density and the residual stress. It was also confirmed that the effect of the heat treatment was excellent given that impurities were effectively removed by this process.