In this process on the InGaP/InAlGaP material system, annealing has improved the performance of the laser devices. Adding the results we achieved before from orange and yellow devices,8,18,19 the results can be explained if we split the process into three subprocesses. The first subprocess is the creation of defects. These defects are created at the interface of the capping dielectric-laser interface and propagate throughout the laser structure. The point defects are created due to the difference in expansion coefficients.20 Defects, created during annealing, increase the nonradiative recombination centers and the optical losses for light propagation inside the structure. Such effects have already been discussed in Ref. 21. We believe the defects created during the annealing process are responsible for the increase in in the annealed devices. The amount of defects can be controlled by reducing the annealing time or reducing the applied strain from the dielectric film. The second subprocess is the interdiffusion of group-III atoms between the QW and the barriers. As a result, the bandgap of the QW is blueshifted as more Al atoms diffuse into the QW. As the temperature and time are increased, the amount of diffusion increases. These two subprocesses are well known in the literature and expected.22 We have experienced similar effects when applying a large degree of intermixing.8,18 The third subprocess, which we are emphasizing, is the reduction of deep-level traps. The considerable improvement in PL intensity and reduction in FWHM with the enhancement in the threshold current can be related to the reduction in deep-level traps and oxygen-related defects due to the elevated temperature as explained in Ref. 9. However, the improvement we are getting in this work is higher than reported.