Analysis of threshold current density and optical gain in InGaAsP quantum well lasers

Single-mode and multimode quantum well (QW) laser diodes with emission wavelengths λ=1.0 and 1.58 µm, based on MOCVD-grown separate-confinement heterostructures, have been studied. An analysis of the threshold current density and optical gain is made on the basis of experimental dependences of the threshold current and differential quantum efficiency on the cavity length. The threshold current is decomposed into principal components in terms of model approximations taking into account the Auger recombination, ejection of electrons from QWs into waveguide layers, and lateral current spreading to passive regions of a mesa-stripe laser.