Effect of barrier thickness on the luminescence properties of AlAs/GaAs multiple quantum wells grown by molecular beam epitaxy

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Abstract
The influence of barrier layer thickness LB for LB >3 nm on the optical properties of all‐binary AlAs/GaAs multiple quantum well heterostructures (MQWH) is studied by photoluminescence and excitation spectroscopy measurements at 2 K. In contrast to expectation for a simple coupling between the constituent GaAs quantum wells, MQWH samples with thinner barrier layers show excitonic peaks shifted to higher energies and exhibit a larger splitting between the electron to heavy‐hole and electron to light‐hole free excitons. This feature remains for different values of the otherwise constant well width within different series and when a small amount of Al is added to the well. Our detailed experimental data indicate that the mechanism responsible for the high‐energy shift is intrinsic in nature. This unusual feature demonstrates the inadequacy of photoluminescence and excitation spectroscopy to determine well widths accurately.