Photoreflectance study of [111] GaAs/AlGaAs quantum wells at room temperature

The photoreflectance technique has been applied to characterize the interband transitions in a [111]A GaAs/AlxGa1-xAs multiple quantum well at room temperature. The sample was grown by atmospheric pressure metalorganic vapour phase epitaxy technique on a [111]A oriented GaAs substrate. High-resolution X-ray diffractometry was used to assess the crystal quality and obtain structural information. To fit the photoreflectance spectrum we used the Aspnes third derivative functional form. The features in the spectrum are assigned to the various optical transitions between electron and hole states with the same index and to the transition of AlGaAs barriers. Our data are consistent with a conduction-band offset of 0.65 and provide a direct determination of the x value.