Characterization of an Asymmetric Triangular Multiple Quantum Well, by Variable Angle Spectroscopic Ellipsometry

Variable angle spectroscopic ellipsometry (VASE) was used to characterize a 20 period GaAs/Al(x)Ga(1-x)As multiple quantum well structure, grown by molecular beam epitaxy. The barriers were nominally 200 Å Al(.25)Ga(.75)As, and the well regions were grown to approximate a linearly graded composition, from x=0 to x=0.25, with total well width 200 Å. VASE data in the E1, E1,+Δ1. region were analyzed using four different models. It was founcЃ that the dielectric function of the cap GaAs layer was shifted to higher energy with respect to the bulk GaAs dielectric function.