Dielectric function effects due to isovalent monolayers of III-elements buried in GaAs, GaP, and AlGaAs

Ellipsometric measurements have been made at room temperature on MOVPE-grown InAs monolayers (ML) (0.5 to 1 ML) in GaAs around the fundamental gap E0 and the critical point (CP) E1 of the material GaAs and on MOVPE-grown InP MLs (0.5 to 1 ML) in GaP around the GaP direct gap. Due to the introduction of monolayer films, the optical properties of the host material are strongly modified as a function of the monolayer material and thickness and of the substrate misorientation. To our knowledge up to now the modifications of the optical properties of the system InP in GaP could only be observed by ellipsometric measurements.