The effect of thermal annealing on the optical properties of Mg-doped zincblende GaN epilayers

The effects of thermal annealing on the optical properties of Mg doped cubic zinc-blende GaN epilayers grown by metalorganic chemical vapor deposition on 3C-SiC/Si (001) substrates are investigated. The photoluminescence spectra show near band edge features and a blue luminescence band that depend on Mg concentration, temperature and excitation power density. Annealing the sample in a N2 atmosphere causes the intensity of the blue band to increase by a factor of 5. Power dependent photoluminescence measurements show a reduction in the laser excitation density required for saturation of the blue band after annealing, indicating an increase in the recombination lifetime. Time decay measurements confirm this increase, which is attributed to a reduction in the concentration of non-radiative defects after annealing. The results presented here are compared to those reported previously for Mg-doped hexagonal wurtzite GaN.