Effects of carbon impurity on GaAs/AlGaAs multiple quantum well lasers grown by molecular beam epitaxy

The fabrication of low threshold current GaAs/AlGaAs gradient index separate confinement triple quantum well lasers grown on a substrate misoriented a few degree off (100) toward ⟨111⟩A in a high CO background is investigated. It is found that the threshold current could be reduced from 32.5 mA to 15.7 mA by tilting the substrate 6°. The photoluminescence results reveal that a carbon impurity, like oxygen, could also be incorporated and trapped at and near AlGaAs/GaAs interfaces during growth and result in excessive scattering and loss and thus a high threshold current. Substrate misorientation for 6° toward ⟨111⟩A could reduce the incorporation of the carbon impurity to an unobservable level