Carbon redistribution and precipitation in high temperature ion-implanted strained Si/SiGe/Si multi-layered structures

Abstract

We report on the segregation of carbon atoms and structural transformations in strained multilayered Si/SiGe/Si structures after molecular-beam epitaxial (MBE) growth, carbon ion implantation and thermal treatment at different conditions. The idea behind this study was that due to their specific strain distribution, pseudomorphic layers of Si/SiGe promote spatial separation of vacancies and interstitials followed by segregation of foreign dopant atoms. High temperature ion implantation was used for injection of carbon atoms as well as point defects in the strained layers. The defects were investigated by transmission electron microscopy (TEM), dopant depth profiles by secondary-ion-mass spectrometry (SIMS), and optical properties by Raman scattering measurements. Based on SIMS data we demonstrate anomalous redistribution of the implanted carbon atoms around the strained SiGe/Si layers which results in their accumulation on the Si side and depletion on the SiGe side of the structure. The TEM study demonstrates formation of plate-like defects, stacking faults and thin carbon-precipitated flakes distributed along the Si/SiGe interfaces. Raman spectra reveal peaks at 1600 and 2700cm−1 which might be associated with carbon-related phases. The concept of strain-enhanced separation of point defects and dopant precipitation is discussed.