Optimization of AlGaAs barrier for InGaAs quantum wells emitting in the near infrared

The results of a study aimed at optimizing the optical properties of InGaAs quantum well structures by employing different barrier designs are presented. Single rectangular InGaAs quantum wells with approximately 21% indium and AlGaAs barriers, with different Al content 12, 20 and 30%, were theoretically modelled using the next nano 3 software to calculate band edges and levels in the quantum wells. A series of samples were grown using molecular beam epitaxy to clarify the influence of the Al fraction in the AlGaAs barriers on the optical properties of the quantum structures. Atomic force microscopy measurements were used to evaluate the surface roughness of the grown structures, while photoluminescence investigations provided insight into the optical quality and carrier confinement effects. The investigations revealed that the introduction of AlGaAs barriers resulted in an increased carrier confinement inside of the quantum well, but consequently resulted in the degradation of the InGaAs quantum well quality with the increase of aluminium content in the barrier. It was determined that a barrier with 12% of Al can be used to balance these effects, by providing a sufficient confinement, while retaining a satisfactory crystalline quality of the quantum structures.