Light Scattering From Ultrathin Si And Ge Layers

Abstract

We describe the use of vibrational Raman spectroscopy to characterize ultra-thin crystalline Ge and Si layers grown by molecular beam epitaxy on Si(100) substrates. Samples have been studied where the Ge or Si layer thickness is less than 1 nm. The Ge layers were grown on Si(100) and covered by a thin silicon cap layer. Thin Si layers were grown on thick, relaxed Ge layers deposited on Si(100). The crystalline Si layer was capped by epitaxial Ge and a thin layer of amorphous Si for protection against oxidation. In spite of signals from the substate and the cap layer that are orders of magnitude stronger than the Raman scattering from the buried layer of interest, Raman scattering provides information about the crystalline quality of the epitaxial growth, the abruptness of the interfaces between the different layers, the strain in the layers and the electronic structure of the layers being studied.