Excitons localization effects in GaAsN/GaAs epilayers grown by MOCVD

Optical studies of GaAs1−xNx/GaAs epilayers grown by metal-organic chemical vapour deposition (MOCVD), with low nitrogen concentration (1.65% and 2.2%), have been achieved by a number of optical techniques such as photoluminescence (PL), photoreflectance (PR) spectroscopies and time-resolved PL (TR-PL) measurements in the nanosecond range. It has been shown that the increase of the nitrogen fraction causes a red shift of the PL emission band compared to the GaAs one. TR-PL results at 12 K reveal that the decay time is clearly dependent on the emission energy. It increases for lower emission energy. From the temperature PL decay lifetime study, we suggest that PL emission is dominated by the recombination of localized excitons trapped by potential fluctuations of the near band edge induced by compositional fluctuations in GaAsN epilayer.