The effect of In segregation on the PLE spectra of InxGa1-xAs/GaAs multiple quantum wells

In this paper we have used the simple model for In segregation presented by Muraki et al. [Appl. Phys. Lett. 61, 557 (1992)] to calculate the profiles for In content in a series of InxGa1-xAs/GaAs MQWs. The resulting potential profiles were calculated, and the envelope function approximation was used in a transfer matrix formalism, to calculate transition energies and overlap integrals. Photoluminescence excitation spectroscopy (PLE) spectra were calculated, and their variation with the amount of In segregation was investigated. We found that while the confined levels shift towards higher energies, the above-barrier levels shift in the opposite direction, resulting in that the calculated PLE spectra "contract" around similar to 1.51 eV. We also measured the PLE spectra of two samples grown at different temperatures and used the segregation ratio R as a fitting parameter. For the sample grown at similar to 500 degrees C we found that less than 80% of the impinging In atoms segregate, while for the sample grown at similar to 520 degrees C the fitted R is 93% when no re-evaporation of the In atoms was assumed.