Optical properties of InP from infrared to vacuum ultraviolet studied by spectroscopic ellipsometry

Abstract The optical properties of an epitaxial indium phosphide (InP) film deposited on an Fe compensated InP (InP:Fe) wafer have been measured at room temperature by ex-situ spectroscopic ellipsometry over a spectral range of 0.038–8.5 eV. The complex dielectric function spectra, e (E) = e1 (E) + ie2 (E), have been determined by fitting a parametric model to the experimental ellipsometric data. Kramers-Kronig consistent parameterizations have been applied to describe interband transitions and defect-based sub-bandgap absorption in the 0.73–8.5 eV spectral range, and both phonon modes and free carrier properties in the 0.038–0.73 eV range. Spectra in e from 0.73–8.5 eV shows ten higher energy interband critical point transitions at 1.36, 1.42, 3.14, 3.34, 4.71, 4.97, 5.88, 6.45, 7.88, and 8.22 eV. The direct band gap energy of 1.37 eV and Urbach energy 46 meV are also determined from spectra in e. A strong optical phonon mode is identified near 305 cm−1. Electronic transport properties, carrier concentration (N) and mobility (μ), calculated from Drude model with N = 1.9 × 1018 cm−3 and μ = 1559 cm2/Vs agree well with direct electrical Hall effect measurement values of N = 2.2 × 1018 cm−3 and μ = 1590 cm2/Vs. A parameterization of e from 0.038 to 8.5 eV for the epitaxial InP film is reported.