Effect of rapid thermal annealing on the optical properties of MBE growth GaNAs films

We report the effect of rapid thermal annealing (RTA) on the optical properties of GaN0.01As0.99 samples grown by molecular beam epitaxy. In particular, a blueshift of the PL peak energy is observed when annealing the samples at 650-900 degrees C. Samples annealed showed pronounced enhancement in PL intensity as compared to the as-grown sample, and 850 degrees C is proposed as the optimum RTA temperature. The results are examined as a consequence of RTA-induced nitrogen diffusion inside the GaN0.01As0.99 material rather than diffusion out of the alloy, which homogenizes initial nitrogen composition fluctuations. In addition, for photo-modulated reflectance (PR) spectra of RTA samples, the fundamental band gap transition (Eo) and the transition from the spin-orbit split-off valence band (E-0 + Delta(0)) are observed. Both of the two transitions increase with increasing annealing temperature. (c) 2006 Published by Elsevier B.V.