PHOTOLUMINESCENCE AND PHOTOREFLECTANCE FROM GAAS ALAS MULTIPLE-QUANTUM WELLS/

Photoluminescence (PL) and photoreflectance (PR) measurements have bee n performed to investigate the intermixing behavior of Al and Ga in Ga As/AlAs multiple quantum wells (MQWs) grown by molecular-beam epitaxy and treated by rapid thermal annealing. These results indicate that th e magnitude of the disordering for a GaAs/AlAs MQW increases as the la yer thickness increases. When the GaAs/AlAs MQWs with layer thicknesse s of 34 Angstrom are annealed at 950 degrees 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 domina ntly the Gamma-valley direct transition, and PR signals show that the peaks originating from the interband transitions disappear. The observ ed increases of the full width at half-maximum (FWHM) in the PL spectr a for the annealed GaAs/AlAs MQWs originate from the nonuniformity of the intermixing as a function of depth, and the decrease of FWHM in th e PL spectra for the GaAs/AlAs MQWs annealed for longer times is due t o the formation of Al0.45Ga0.55As alloys in the GaAs/AlAs MQWs. (C) 19 95 American Institute of Physics.