Photoluminescence and photoreflectance from GaAs/AlAs multiple quantum wells

Photoluminescence (PL) and photoreflectance (PR) measurements have been performed to investigate the intermixing behavior of Al and Ga in GaAs/AlAs multiple quantum wells (MQWs) grown by molecular-beam epitaxy and treated by rapid thermal annealing. These results indicate that the magnitude of the disordering for a GaAs/AlAs MQW increases as the layer thickness increases. When the GaAs/AlAs MQWs with layer thicknesses of 34 Å are annealed at 950 °C for 10 s, the GaAs/AlAs MQWs are totally intermixed, resulting in a formation of an Al0.45Ga0.55As alloy. For the intermixed GaAs/AlAs MQWs, PL spectra show dominantly the Γ-valley direct transition, and PR signals show that the peaks originating from the interband transitions disappear. The observed increases of the full width at half-maximum (FWHM) in the PL spectra for the annealed GaAs/AlAs MQWs originate from the nonuniformity of the intermixing as a function of depth, and the decrease of FWHM in the PL spectra for the GaAs/AlAs MQWs annealed for longer times is due to the formation of Al0.45Ga0.55As alloys in the GaAs/AlAs MQWs.