Photoluminescence and photoreflectance studies in GaAs/AlxGa1-xAs heterojunctions in the low Al concentration range

We present results on the optical characterization of AlxGa1-xAs epitaxial layers grown by liquid phase epitaxy with low aluminum concentrations in th e range 0.01 less than or equal to x less than or equal to 0.2. By using th e low temperature photoluminescence spectroscopy (PL) we measured the PL sp ectra and from the analysis of the excitonic recombination band we were abl e to characterize the crystalline quality of the layers. From the PL spectr a we got information also about the presence of impurities and defects in t he layers. The photoreflectance spectroscopy was used to determine the band gap energy of the AlGaAs layer and to study the interface with the GaAs su bstrate.