Optical gain and threshold properties of strained InGaAlAs/AlGaAs quantum wells for 850-nm vertical-cavity surface-emitting lasers

The valence subband structures, optical gain spectra, transparency carrier densities, and transparency radiative current densities of different compressively strained InGaAlAs quantum wells with Al_0.3Ga_0.7As barriers are systematically investigated using a 6 × 6 k · p Hamiltonian including the heavy hole, light hole, and spin-orbit splitting bands. The results of numerical calculations show that the maximum optical gain, transparency carrier densities, transparency radiative current densities, and differential gain of InGaAlAs quantum wells can be enhanced by introducing more compressive strain in quantum wells. However, further improvement of the optical properties of InGaAlAs quantum wells becomes minimal when the compressive strain is higher than approximately 1.5%. The simulation results suggest that the compressively strained InGaAlAs quantum wells are of advantages for application in high-speed 850-nm vertical-cavity surface-emitting lasers.