Excitonic luminescence and absorption in dilute GaAs_1-xN_x alloy (x<0.3%)

Dilute GaAs_1-xN_x alloys (x<0.3%) were grown by metalorganic vapor phase epitaxy to investigate their photoluminescence and photoluminescence excitation characteristics. Photoluminescence excitation spectra show clear excitonic absorption peaks at low temperatures and their peak energy drastically decreases with increasing nitrogen concentration due to the band-gap bowing in the GaAsN system. This result indicates that the band-gap bowing starts at a nitrogen concentration as low as 10 cm^-3 and its bowing parameter is -22 eV. According to this band-gap bowing, the GaAsN alloys show two photoluminescence lines whose peak energy decreases with increasing nitrogen concentration. Their dependence on the nitrogen concentration suggests that these lines correspond to excitonic and carbon-related transitions in the GaAsN alloy.