Optical properties of SixGe1−x single crystals grown by liquid phase diffusion

In this article, we present measurements for the pseudo-optical functions of germanium-rich SixGe1−x (0.000≤x≤0.100) single-crystals (grown by Liquid Phase Diffusion; LPD) using spectroscopic ellipsometry and photoreflectance techniques in the energy range of 1.72–3.20 eV. The E1 interband transition energies are obtained from numerically differentiated optical spectra for various crystal compositions. It was shown that the values of E1 interband transition energy determined by both the ellipsometric and photoreflectance measurements for germanium-rich SixGe1−x single-crystals are in agreement with those of bulk SiGe crystals reported in the literature [21–24]. The interband transition energies are found to be in the range of 2.100 and 2.215 eV for the composition values of 0.000≤x≤0.100. The surface morphology of the crystals assayed via atomic force microscopy shows fibrous surfaces with the average grain size of 250 nm. The measured root-mean-square (rms) roughness and maximum height are in the range of 3.78–5.40 and 32.42–67.84 nm, respectively, with increasing germanium composition.