InP optical constants between 0.75 and 5.0 eV determined by variable-angle spectroscopic ellipsometry

Abstract

Using variable-angle spectroscopic ellipsometry (VASE) InP optical constants for photon energies have been determined in the range from 0.75 to 5.0 eV, which includes the fundamental gap at 1.35 eV. Above 1.5 eV the results are consistent with previously measured pseudovalues from an oxide-stripped sample when a very thin residual overlayer is accounted for. They are also shown to be compatible with previously published prism measurements of refractive index below the band gap. Real and imaginary parts of the dielectric function are shown to be Kramers–Kronig (KK) self-consistent above the gap, and the KK analysis was used to extend the dielectric function below the measurement range to 0.5 eV. The assumptions underlying biased fitting of VASE data and the importance of variable-angle measurements were investigated. The detection and significance of systematic errors for general VASE data analysis were also investigated, especially with regard to fit parameter confidence limits.