High-pressure high-temperature annealing of ion-implanted GaN films monitored by visible and ultraviolet micro-Raman scattering

Visible and ultraviolet micro-Raman scattering was employed to monitor the high-pressure high-temperature annealing of Mg/P-implanted GaN films. The results illustrate the use of Raman scattering to monitor processing of GaN where fast feedback is required. Temperatures up to 1500°C with nitrogen overpressures of 1-1.5 GPa were used during the annealing. The crystalline quality, the strain, and the free carrier concentration in the ion-implanted GaN films was monitored, averaged over the layer thickness and in a 40-nm-thin surface layer of the sample. Annealing temperatures of 1400-1500°C were found to result in the nearly full recovery of the crystalline quality of ion-implanted GaN. No significant surface degradation occurred during the annealing. High nitrogen overpressures proved very effective in preventing the nitrogen cut-diffusion from the GaN surface at high temperatures. Strain was introduced during the annealing. Changes in the free carrier concentration were studied.