Electronic and optical properties of compressively strained GaInNAs/GaAs quantum-well lasers

The electronic and optical properties of compressively strained GaInNAs/GaAs quantum-well (QW) lasers are investigated using the multiband effective-mass theory. We also take into account the many-body effects on the optical gain spectrum. The optical gain is largely improved with decreasing well width because of an increase in the quasi-Fermi energy separation. On the other hand, the matrix elements are not responsible for the increase in the optical gain. For a given threshold optical gain, the radiative current density contribution to the threshold current density increases when the well width increases. The threshold current density decreases with increasing well width and becomes nearly constant, irrespective of the strain, as the well width exceeds 80 A. The saturation is believed to be attributed to the fact that the improvement in the electron-hole overlap for wider wells is compensated for exactly by the decrease in the quasi-Fermi energy separation.