Blue shift in InGaAsN/GaAs quantum wells with different width

Three InGaAsN/GaAs QWs with well widths of 3, 5 and 9 nm were grown in one single sample with a GaAs barrier width of 35 nm under the same growth conditions. Post-growth rapid thermal annealing (RTA) was applied at 700°C on this sample and photoluminescence (PL) was measured after different RTA times. It was observed that the blue shifts (BS) were the same, up to ∼15 meV in the first 30 s, for all three QWs; after this the BS of the 9-nm QW saturated very soon at 24 meV and the BSs of 5-nm and 3-nm QWs were saturated much more slowly at more than 45 meV and 57 meV, respectively. There are at least two factors that affect the BS: interdiffusion and short-range order (SRO). SRO is started and saturated much faster than interdiffusion during annealing.