Detailed analysis of room-temperature photoreflectance of strained InxGa1−xAs/AlyGa1−yAs undoped single quantum wells

We report a detailed analysis of room-temperature photoreflectance data of four InxGa1−xAs/AlyGa1−yAs undoped strained single quantum wells with x≊0.20 and y≊0, 0.05, 0.10, and 0.20. We have compared our results with theoretical calculations based on an effective mass formalism, where possible variations of well and barrier composition and thickness have been included. For all the samples studied we have identified both allowed and forbidden transitions in the spectra and obtain good fits assuming a conduction-band offset Qc of 60%±5%. This detailed analysis shows for the first time that room-temperature photoreflectance measurements alone can be used to determine the well composition and thickness together with the barrier composition and the barrier offset.