Strained state of the layer system depending on the SiGe layer thickness by micro-Raman mapping

Abstract

Micro-Raman scattering experiments, including Raman spectroscopy and microscopy, have been carried out to study the strain state of the Si 0.75Ge 0.25 films using the low-temperature Si (LT-Si) buffer layers. SiGe layers with different thickness of 1000, 3000 and 5000 Å on LT-Si were grown on Si (0 0 1) substrates by gas-source molecular beam epitaxy (MBE). The Raman-generated images have provided a direct picture of the strain state of the SiGe layer and Si substrate with SiGe thickness. The experimental results give us evidence that the change of strain state in the SiGe film and the Si substrate with the SiGe thickness is ascribed to the LT-Si buffer layer, which can effectively adjust the strain mismatch. This function is similar to compliant effect as a thin freestanding substrate.