An Optically Effective Intermediate Layer Between Epitaxial Silicon and Spinel or Sapphire

Abstract

The existence of an optically effective intermediate layer between epitaxial silicon and spinel or sapphire has been proved. By measuring the optical and geometric thickness of the films as a function of film thickness a difference in the thickness values was found which could be interpreted as the thickness of an intermediate layer. This layer was also measured directly with a stylus tracer yielding a thickness of about 40 nm. Reflection electron diffraction and secondary ion mass spectroscopy were performed. A growth model for the silicon films is proposed which assumes that aluminum silicates will be formed due to reactions with the substrate as long as the substrate surface is uncovered. Despite or possibly because of this existing intermediate layer good epitaxial silicon films are obtained.