Thermionic emission and photoluminescence studies of the energy states of GaAs/AlAs superlattices

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Abstract
We have performed thermionic emission measurements on doped GaAs/AlAs superlattices and photoluminescence measurements on a series of undoped GaAs/AlAs superlattices having different well widths. Using these techniques, we determined that the energy states in the GaAs wells are bounded by the Γ minimum of the AlAs barriers, and that the X minimum instead of the Γ minimum in the AlAs layer is the relevant barrier height for the current transport in our experiment. From the magnitude of the thermionic emission current, the coupling between the Γ and X states is shown to be approximately 100 times weaker than the Γ-Γ coupling, which is consistent with the theoretical tight-binding model.