STRAIN STUDIES OF SILICON-GERMANIUM EPILAYERS ON SILICON SUBSTRATES USING RAMAN-SPECTROSCOPY

Atmospheric pressure chemical vapor deposition techniques have been us ed to grow electronic quality Si-Ge epilayers on Si substrates. The de gree of tetragonal strain in the layers has been determined using Rama n spectroscopy. The relative energy shift of the Si-Si phonon line ass ociated with the Si1-xGex epilayers from a pseudoalloy of the same com position was used as a quantitative measure of the strain. Layer growt h was found to be almost commensurate with the Si substrates for thick nesses in the region of approximately 100 nm. For x congruent-to 0.1 t he resulting films were highly strained and homogeneous. The strain di minished with increasing thickness and it was estimated that a layer w ould be fully relaxed when the thickness exceeded 3000 nm. The phonon linewidths provided information on the epilayer and interface quality.