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(degree)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.