GaAs/AlGaAs Superlattice Characterization By Variable Angle Spectroscopic Ellipsometry

Abstract

Variable angle of incidence spectroscopic ellipsometry (VASE) was used to determine the thickness, alloy composition, and growth quality of multilayer samples. These samples contained a single quantum well grown on a GaAs/AlGaAs superlattice. The superlattice layers were modeled as a bulk Al GaAs layer of unknown composition and thickness. A data fitting procedure allowed the variation of five layer thicknesses and two alloy compositions in a regression analysis. Extremely good data fits of the ellipsometric parameters * and A were realized in the 1.55 to 3.54 eV spectral range. Computer generations of the ellipsometric parameters were performed, and were compared with experimental results. The e-hh(1), e-lh (1), and e-hh(2) exciton transitions were observed in the VASE data measured at room temperature. VASE has thus provided a nondestructive and highly effective technique for characterizing intricate multilayered structures.