Enhanced luminescence from AlGaAs/GaAs single quantum well structures through improved interfaces

Abstract

In single GaAs quantum wells sandwiched between relatively thick AlxGa1−xAs, only weak photoluminescence which is dominated by extrinsic processes is observed. This is attributed to a degraded interface at the bottom AlGaAs/GaAs heterojunction. The situation worsens when the thickness of the bottom AlGaAs layer is increased, the GaAs thickness is reduced, or the Al mole fraction is increased. Inserting a graded three-period superlattice between the AlGaAs and GaAs quantum well at the bottom interface causes the intensity of the photoluminescence associated with exciton recombination to increase to more than 160 times that in the conventional quantum well. Furthermore, the impurity related photoluminescence from the improved quantum well is almost entirely absent; the photoluminescence is dominated by the recombination of the ground state n=1 heavy-hole free exciton. This dramatic improvement is indicative of the improvement of the interface resulting from the insertion of a thin superlattice.