Tensile strain and threshold currents in GaAsP-AlGaAs single-quantum-well lasers

The effects of tensile strain on threshold current in GaAsP-AlGaAs quantum well lasers are studied theoretically and experimentally. A comprehensive model for the light-current characteristics of separate-confinement strained-layer lasers, which is based on a six-band Luttinger-Kohn valence dispersion model, is first developed, Theoretical and experimental results for broad stripe single-well laser diodes with a constant well width of 115 Angstrom are then presented, Experimentally observed variations in threshold currents and TE/TM polarization switching are accurately described by the model for phosphorus compositions in the quantum-wed ranging from 0 to 0.30 and cavity lengths ranging from 300 to 1500 mu m, Constant-gain contours generated from the theoretical model are shown to provide a simple and powerful guide to various regimes of operation, Our studies show that tensile strain-related effects lower threshold currents in GaAsP-AlGaAs only in the high gain (short cavity) regime, and suggest more generally that the threshold advantages offered by tensile strain are conditional.