Annealing effect of the InAs dot-in-well structure grown by MBE

•Annealing effect has been studied for the InAs dot-in-well structure.•The QDs with large size in DWELL are vulnerable to the annealing process above 550 °C.•Lasing wavelength of 1.31 μm was achieved by growing the top cladding layer at 540 °C.•Lasing wavelength of 1.18 μm was obtained by growing the top cladding layer at 600 °C. We have demonstrated that in situ annealing effect has to be taken into account in order to realize the 1.31 μm InAs quantum dot (QD) lasers with the dot-in-well (DWELL) structure. The photoluminescence (PL) properties have been investigated for the InAs DWELL samples annealed at different temperatures in situ, simulating the annealing process during the growth of the top cladding AlGaAs layer in the laser structure. The QDs with large size in the DWELL structure are vulnerable to the annealing process at temperatures above 550 °C, revealed by the drastic change in the PL spectra. However, the DWELL structure is stable during the annealing process at 540 °C for three hours. The thermal stability of the QDs in the DWELL structure has to be considered in the growth of QD lasers for long wavelength operation.