Calculation of the infrared reflection spectra of inhomogeneously doped silicon semiconductor layers at an arbitrary angle of incidence

A method is developed, based on the optical admittance, to calculate reflectance and transmittance at arbitrary angle of incidence of stratified media with arbitrary refractive index profiles. For n-type silicon samples, calculated and measured IR spectra are shown. In the case of a lightly doped epitaxial layer on heavily doped substrate, measurement in π polarization at the Brewster angle of the layer produces a spectrum which is free of the interference waves due to the layer and gives direct information about the profile beneath the layer. Such spectra could be used for the characterization of the transition layer between the epitaxial layer and the substrate.