Mechanism of photoluminescence blue shift in InGaAsN/GaAs quantum wells during annealing

InGaAsN/GaAs 3-QWs with different well widths of 3, 5 and 9 nm were grown in one wafer. By studying the thermal annealing and photoluminescence (PL), we observed that, (1) the blue shifts (BS) were the same of up to ∼15 meV in the first 30 s for all 3 QWs; (2) after this, the BS of the 9-nm QW saturated very soon at 24 meV and the BSs of 5- and 3-nm QW were saturated much more slowly at more than 45 and 57 meV, respectively. There are at least two factors affect the BS: inter-diffusion and short-range ordered (SRO). SRO is started and saturated much faster than inter-diffusion during annealing.