Dominant direct transitions in annealed GaAsrAlAs multiple quantum wells

Photoluminescence PL.and photoreflectance PR.measurements were performed in order to investigate the formation of the Al0.45Ga0.55As alloys in the GaAsrAlAs multiple quantum wells MQWs.grown by molecular beam epitaxy MBE. and treated by rapid thermal annealing. The results of the PL measurements show that a G-valley direct transition is dominant in annealed GaAsrAlAs MQWs while an X-valley indirect transition is typical in as-MBE-grown Al0.45Ga0.55AsrGaAs. This result indicates that the PL spectrum for the Al xGa1yx As alloy structure with a high Al mole fraction formed by annealing GaAsrAlAs MQWs shows direct transitions, which holds promise for potential applications in optoelectronic devices. q1999 Published by Elsevier Science B.V. All rights reserved