Electric field response of a semiconductor superlattice optical mirror from electroreflectance spectra

摘要

We report lowhyphen;field electroreflectance (ER) spectra of an allhyphen;semiconductor multilayer optical mirror structure. The structure, consisting of alternating blocks of AlAs/Al0.5Ga0.5As and Al0.5Ga0.5As/GaAs multiple quantum well layers, was grown by molecular beam epitaxy without wafer rotation. Thickness variations across the wafer produce a positionhyphen;dependent reflectance spectrum. The observed line shape of the bandhyphen;edge exciton depends on its wavelength position relative to the mirror spectrum and cannot be explained by ordinary ER theory, due to the rapidly varying background mirror reflectance. Computer simulations, using the matrix method to calculate the reflectance for different layer thicknesses and exciton energies, agree qualitatively with the data. A strong enhancement in ER response is predicted near the minima in the mirror spectrum. This enhancement is important in electohyphen;optic reflectance modulators.