Carrier distribution, gain, and lasing in 1.3-μm InAs-InGaAs quantum-dot lasers

In this paper, we present the results of a theoretical model built to describe the temperature-dependent lasing characteristics of InAs-InGaAs quantum-dot (QD) lasers operating at 1.3 μm. From the model, we find that traditional carrier distribution theories are inadequate to describe the performance of these lasers. We therefore introduce an improved model that allows for both free carriers and excitons in the dots. The new model provides threshold current and characteristic temperature T₀ values that are in good agreement with experimental data. The results of our modeling reveal that, while it is the excitons that mainly contribute to the gain, the ratio of excitons to free carriers significantly affect the T₀ of QD lasers. Our model results also indicate that the wetting layer current plays little role in QD laser performance. In addition, the model correctly predicts other experimental observations such as; increased T₀ for increased number of QD layers and p-doped structures, and the oscillatory behavior of T₀, lending further credibility to the model.