Long time aging effect on Be-implanted GaN epitaxial layer

Be-implanted GaN thin films grown by low-pressure Metalorganic Chemical Vapor Deposition (LP-MOCVD), the postimplantation rapid thermal annealing (RTA) samples and the postimplantation RTA samples after 18 years’ room temperature (RT) aging were investigated by Resonant Raman scattering (RRS). It was observed that the Resonant Raman scattering intensity is most enhanced in the 4th order A1 (LO) mode in the after aging sample rather than both the 4th and 5th order A1(LO) mode at different temperatures in the postimplantation RTA sample, which is attributed to a different prominent laser excited emission involved in the RRS processes in the sample before and after aging. A jump step of the intensities of RRS modes was observed at 170 K. Based on the temperature dependent and power dependent RRS spectra, we estimate quantitatively the properties of the optical emission participated in RRS processes below and above this temperature, with the assumption that the intensity of the RRS modes is linearly proportional to the intensity of the optical emission involved in it. We obtained the activation energy of 65 meV and 85 meV for two emissions, respectively, and confirmed both emissions are not band edge related emission with power density dependent RRS spectra. We proposed the dominant optical emission changed from band edge emission to dopant related emission after aging. This study provides an evidence of evolution of optical properties and microstructures in postimplantation RTA GaN epilayers over long time RT aging, which could be a benefit to studying reliability control of devices based on this material.