Rapid thermal annealing of GaN _xAs _1-x grown by radio-frequency plasma assisted molecular beam epitaxy and its effect on photoluminescence

The effect of rapid thermal annealing (RTA) on GaNAs films grown on GaAs (100) substrates by radio frequency plasma-assisted solid source molecular beam epitaxy was investigated by low-temperature photoluminescence (PL) and high-resolution x-ray diffraction (HR-XRD) measurements. GaNAs samples with N content of 1.3% and 2.2% determined by experimental curve fitting of x-ray rocking curve with the dynamical diffraction theory, exhibit an overall blueshift in energy of 67.7 meV and an intermediate redshift of 42.2 meV in the PL spectra when subjected to RTA at 525-850°C for 10 min. The results suggest that the GaNAs layer may have undergone an intermediate substitutional-interstitial diffusion in addition to purely outdiffusion of nitrogen atoms. Samples annealed at 700-750°C showed 1.7-2.1 times improvement in integrated PL intensity and 1.6-1.8 times reduction in PL full width half maximum as compared to the as-grown sample. The HR-XRD results show no significant changes in GaNAs lattice parameter between the as-grown and annealed samples. This indicates the samples are thermally stable, with low overall nitrogen outdiffusion. The results have significant implication on the growth and postgrowth treatment of GaNAs material for high performance optoelectronic device application.