Optimization of oxide-confinement and active layers for high-speed 850-nm VCSELs

Vertical-cavity surface-emitting lasers with variant compressively strained InGaAlAs quantum wells have been investigated. The valence band structures, optical gain spectra, and threshold properties of InGaAlAs/AlGaAs quantum wells are compared and analyzed. The simulation results indicate that the characteristics of InGaAlAs quantum wells can be improved by increasing the amount of compressive strain in quantum well. Furthermore, the properties of VCSELs with these compressively strained InGaAlAs quantum welk are studied numerically. The results of numerical calculations show that the threshold current and maximum output power can be enhanced by using higher compressively strained InGaAlAs quantum well. However, when the compressive strain is larger than about 1.5%, further improvement of the laser performance becomes minimal. The effects of the position and aperture size of the oxide-confinement layers on the laser performance are also investigated. Variation of the oxide layer design is shown to affect the current distribution which makes the temperature in the active region different. It is the main reason for the power roll-off in the VCSEL devices.