Dependence of polarization mode and threshold current on tensile strain in AIGaAs/GaAsP quantum well lasers

Trends in threshold current and other device characteristics were measured in a series of tensile-strained Al_0.34Ga_0.66As/GaAs_1-yP_y separate confinement heterostructure single quantum-well (SCH-SQW) lasers. Tensile strain in the wells was varied between 0 and 1% by changing the phosphorous composition from 0 to 30%. For short (300 μm) cavity length, devices with 15% P demonstrated the lowest threshold current density of 330 A/cm². For longer cavities, the threshold was lowest (195 A/cm²) for nearly lattice-matched devices, and increased slightly with higher P compositions up to 18% (222 A/cm²). The output of the tensile-strained lasers is transverse magnetic (TM) polarized for devices with ≥9% P in the well.