Analysing the thermal-annealing-induced photoluminescence blueshifts for GaInNAs/GaAs quantum wells: a genetic algorithm based approach
In this paper, we discuss two blueshift mechanisms that are present during the rapid thermal annealing of GaInNAs quantum wells (QWs). A GaInNAs/GaAs sample was grown using molecular beam epitaxy with a GaAs cap layer. Photoluminescence (PL) peak wavelengths from the QWs were measured for annealing temperatures, 680–800 °C, and annealing time up to 3 h. An experimental PL blueshift has been analysed for individual blueshift components due to the reorganization of the N-bonding configuration and the In/Ga interdiffusion across the QW interfaces, using a genetic algorithm based approach. It is found that the interdiffusion-induced blueshift is unaffected by the nitrogen-bonding configuration if the diffusion length is less than 2 nm. However, for larger diffusion lengths, the QW with gallium-rich N-bonding configuration shows a larger blueshift. Our calculations suggest the presence of N–Ga3In1 bonding configuration in the as-grown GaInNAs/GaAs QW, which changes to a mixture of N–Ga3In1 and N–Ga2In2 after annealing. The activation energy for short range order (SRO) is 2.38 eV, which is smaller than that for the interdiffusion process (3.196 eV), indicating that SRO is the dominant mechanism for the PL blueshift at low annealing temperatures and at the beginning of the annealing process.