Determination of optical constants of strained Si_1-xGe_x epitaxial layers in the spectral range 0.75–2.75 eV

Optical characterization of strained Si_1-xGe_x (0≪x≤0.30) heteroepitaxial layers has been performed using a spectroscopic phase modulated ellipsometer in the near infrared to the visible range (0.75–2.75 eV). The dielectric function of the Si_1-xGe_x layers in this spectral range was fitted to an empirical formula with five parameters which were determined using a series of samples with known compositions. Accurate ellipsometry measurement of thickness and composition has been successfully demonstrated using this formula. This study provides a numerical expression for the optical constants of strained Si_1-xGe_x in the spectral range of interest for most optoelectronic applications. © 1997 American Institute of Physics.