Indium migration and controlled lateral bandgap variations in high-power strained layer InGaAs-AlGaAs lasers grown on nonplanar substrates

Strained single quantum well (SQW) InGaAs-AlGaAs graded-index separate confinement heterostructure (GRINSCH) lasers were grown by molecular beam epitaxy over nonplanar (100) oriented substrates. Large variations were observed in the effective bandgap of the strained quantum well as a function of the width of the underlying substrate ridge or groove. These variations are associated with increased In composition in the strained quantum well which arises from incorporation of adatoms migrating from the low growth (311)A side facet to the preferential growth (100) active area facet. The properties of laser structures consisting of two separately contacted segments along the laser cavity with different bandgaps were investigated. Using the segment with the larger bandgap as passive waveguide cavity, its bandtail absorption and characteristic Urbach energy were measured by comparing the transmitted to the directly emitted spontaneous emission