Carbon incorporation in GaAs/Al0.2Ga0.8As triple quantum wells and its effect on laser performance

We report an investigation of the interface quality of the Al0.2Ga0.8As/GaAs triple quantum wells (QWs) grown on the GaAs substrates 0 degrees and 6 degrees off (100) towards [111] A at a high CO environment, using the photoluminescence technique. The direct correlation between the quantum well quality and the performance of lasers which contain such quantum wells as an active region is also reported. It is found that impurity-related photoluminescence is observed only in the sample grown on the exact (100) GaAs substrate but not in the tilted one, as confirmed by temperature dependence results. The full width at half maximum (FWHM) of the intrinsic luminescence is as high as 9.0 meV in the 0 degrees tilted samples and decreases to 3.10 meV in the samples misoriented 6 degrees, indicating a remarkable difference in their interface quality. The impurities incorporated into the interfaces of the QWs are carbon, incorporation of which becomes unobservable by photoluminescence when the quantum wells are grown on substrates misoriented by 6 degrees degrees. The threshold current and quantum efficiency of the laser devices with Al0.2Ga0.8As/GaAs quantum wells as their active region are found to be directly related to the interfacial quality of the quantum wells. (C) 1998 Academic Press.