Optical properties of Si1−xGex/Si thin films

In this paper we study the growth of SiGe thin films (n-type) on c-Si substrate (p-type) by Molecular Beam Epitaxy. High resolution Raman spectroscopy atomic force microscopy and X-ray diffraction are used to characterize the thin epitaxial layers of n-type SiGe thin films. The refractive index \(n\left( \lambda \right)\) and the extinction coefficient \(k\left( \lambda \right)\) of SiGe thin films with various Ge fractions are determined using spectroscopic ellipsometry in the frame of the Forouhi and Bloomer model. The simulation study shows that the refractive index decreases with Ge fraction in the U–V range whereas, the extinction coefficient increases in the visible region. The experimental extracted E_g of SiGe agrees well with the theoretical calculation on the strained SiGe material. The luminescence is characterized by a broad PL band centered at 779 nm.