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 potentia l profiles were calculated, and the envelope function approximation was use d in a transfer matrix formalism, to calculate transition energies and over lap integrals. Photoluminescence excitation spectroscopy (PLE) spectra were calculated, and their variation with the amount of In segregation was inve stigated. We found that while the confined levels shift towards higher ener gies, the above-barrier levels shift in the opposite direction, resulting i n that the calculated PLE spectra "contract" around similar to 1.51 eV. We also measured the PLE spectra of two samples grown at different temperature s and used the segregation ratio R as a fitting parameter. For the sample g rown at similar to 500 degrees C we found that less than 80% of the impingi ng 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.