Low-temperature emission in dilute GaAsN alloys grown by metalorganic vapor phase epitaxy.

We have investigated the optical emission from GaAs1-xNx epilayers with 4.3×10-4<x<0.012. The samples were grown on GaAs(001) substrates by metal-organic vapor phase epitaxy using dimethylhydrazine as the nitrogen precursor. We find that the incorporation of nitrogen in GaAs generates deep radiative centers at around 250 meV below the GaAsN band gap. The defects associated with these centers can be eliminated through an optimization of the growth temperature and reactor pressure, and by postgrowth annealing at 700 °C. We also find that, contrary to what was suggested by Makimoto et al. [Appl. Phys. Lett. 70, 2984 (1997)], the near-gap emission located close to 25 meV below the gap is not related to a free-to-bound transition even in the samples with the lowest nitrogen content. Rather, we associate this emission to excitons bound to overlapping nitrogen clusters. [ABSTRACT FROM AUTHOR]