Advanced optical characterization of AlGaAs/GaAs superlattices for active regions in quantum cascade lasers

Abstract

In this work, AlGaAs/GaAs superlattices with layer composition imitating the active region of quantum cascade lasers emitting in the mid infrared spectral range were investigated. Using optical spectroscopy techniques (photoreflectance and photoluminescence) together with numerical calculations performed within the effective mass approximation, we studied the band structure of the formed conduction minibands including the modification of the wave functions with the external electric field. In addition, the applied growth rates of the GaAs/AlGaAs superlattices have been verified by investigating the Stokes shift between the emission and absorption spectra. Finally, it has been shown that testing the structure imitating the operational laser device might be performed (without the electric field applied) by photoluminescence measurements realized within the Fourier Transformed Infrared Spectroscopy based concept.