Enhancement in excitonic absorption due to overlap in heavy-hole and light-hole excitons in GaAs/InAlGaAs quantum well structures

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Abstract
In this letter we present experimental and theoretical results for excitonic transitions in coherently strained GaAs/InGaAlAs multiquantum well structures grown on a GaAs substrate. Absorption spectra of the structure with the substrate removed show an extremely sharp exciton peak with an absorption constant corresponding to nearly twice the value of that in the lattice-matched GaAs/AlGaAs system. Theoretical calculations suggest that the biaxial tensile strain in the well region, occurring after the substrate is removed, causes the heavy-hole and light-hole exciton states to coincide for a specific composition of the quaternary alloy. A comparison between the experiments and theory is made and the potential for devices based on this phenomenon is discussed.