Optimization of 1.3 mu m InAs/GaAs quantum dot lasers epitaxially grown on silicon: taking the optical loss of metamorphic epilayers into account

Taking the optical loss caused by the metamorphic layers into account, we have proposed an optimization strategy for 1.3 mu m InAs/GaAs quantum dot (QD) laser structures directly grown on silicon. We have investigated the effects of the QD layer number, the thickness and the composition of AlGaAs cladding layers on QD laser performance. The results demonstrate, with respect to the net modal gain and the differential quantum efficiency, that the optimized QD layer number is 7 for lasers grown on silicon, which is different from the optimized number of 5 for the counterparts grown on native substrates. The optimized thickness is obtained for the cladding layers of Al0.4Ga0.6As, Al0.6Ga0.4As and Al0.8Ga0.2As. Further, the optimized QD layer number for the net modal gain is nearly independent of the material gain of active regions. More importantly, the optimization strategy provides a comprehensive method to understand the differences in design between QD laser structures on silicon and those on native substrates.