Excitonic binding energies in diffused-intermixed GaAs/AlAs/AlGaAs double barrier quantum wells

We report a detailed study of the exciton properties in thermally diffused GaAs/AlAs/AlxGa1−xAs double barrier quantum wells (DBQW). The interband transition energies have been calculated with a standard transfer matrix method, while the exciton binding energy is obtained by a variational approach with an elliptic exciton envelope function. It is found that the inserted thin AlAs layer between the GaAs well and the AlGaAs barriers has a substantial effect on the exciton confinement and the intermixing properties. For thin enough AlAs barriers, the exciton binding energy increases for increasing diffusion lengths, reaches a maximum and then decreases gradually. The results show that a DBQW mixes faster than a single QW, due to the additional AlAs layers. Thick AlAs barriers enable the formation of an indirect AlGaAs intermixed well region, and the effects which stem from the indirect band line up are discussed.