Thermal effects in 1.3-μm InAs/GaAs quantum-dot vertical-cavity surface-emitting lasers

Abstract

1.3-μm GaAs/InAs quantum-dot (QD) vertical-cavity surface-emitting lasers (VCSELs) are attracting great interest in the research of laser diodes due to the special merits of the QD structure. However, the performance of QD VCSELs is influenced negatively by their carrier confinement, which suffers a significant degradation due to a serious self-heating effect. The goal of this project is to analyze and characterize the influence of self-heating on the performance of output power in 1.3-μm GaAs/InAs QD VCSELs and to realize the improvement and optimization in device fabrication. This research work includes both theoretical (modeling) and experimental (device processing) approaches. In theoretical study, a self-consistent model comprised of rate equations and the thermal conduction equation was established to analyze the influence of self-heating on the carrier occupation, the quantum efficiency and the output power of 1.3-μm GaAs/InAs QD VCSELs. The simulation results showed that the poor hole confinement in QDs is due to the thin wetting layer, and the increase in the surface density and the layer number of QDs can significantly decrease the self-heating generation and improve the quantum efficiency. The output power of QD VCSELs is mainly determined by the quantum efficiency. A higher output power can be achieved by increasing the number of QD layers and the surface density. However, there exists an optimized number of QD layers (~15) to achieve the highest roll-over output power.