Improved GaAs/AlGaAs single quantum wells through the use of thin superlattice buffers

Abstract

In general, single GaAs quantum wells surrounded by AlxGa1−xAs cladding layers show only weak photoluminescence corresponding to exciton recombination. This is attributed to the poor quality of the AlGaAs in the lower cladding layer resulting in a degraded interface and poor GaAs in the quantum well. The situation gets worse when the thickness of the bottom AlGaAs layer is increased, the GaAs thickness is reduced, or the Al mole fraction is increased. Using a graded three-period superlattice ahead of the quantum well causes the intensity of the photoluminescence associated with exciton recombination to increase to more than 160 times that associated with the conventional structure. This exciton recombination peak is due to either very shallow bound or free-electron recombination and has a full width at half-maximum of only 2 meV.