Dielectric functions and interband transitions of InxAl1 − xP alloys

•We report dielectric functions (ε) of InxAl1 − xP alloys (0 ≤ x ≤ 1).•The ε data were measured by spectroscopic ellipsometry from 1.5 to 6 eV.•The critical points (CPs) are obtained from second-energy-derivatives of the spectra.•We identify CPs from the linear augmented Slater-type orbital band calculation.

We report pseudodielectric functions <ε> from 1.5 to 6.0 eV of InxAl1 − xP ternary alloy films. Data were obtained by spectroscopic ellipsometry on 1.2 μm thick films grown on (001) GaAs substrates by molecular beam epitaxy. Artifacts were minimized by real-time assessment of overlayer removal, leading to accurate representations of the bulk dielectric responses of these materials. Critical-point (CP) energies were obtained from numerically calculated second energy derivatives, and their Brillouin-zone origins identified by band-structure calculations using the linear augmented Slater-type orbital method.