SYNTHESIS OF EPITAXIAL SI1-YCY ALLOYS ON SI(001) WITH HIGH-LEVEL OF NON-USUAL SUBSTITUTIONAL CARBON INCORPORATION

Si1-yCy epilayers have been grown at 600 degrees C on Si(001) associat ing solid source molecular beam epitaxy for Si supply and C2H4 thermal cracking or CH4 ECR (electron cyclotron resonance) H-2 plasma decompo sition as C sources. The samples have been analyzed in situ by X-ray p hotoelectron spectroscopy (XPS), low-energy electron diffraction (LEED ), and X-ray photoelectron diffraction (XPD) and ex situ by Rutherford backscattering (RES), Raman and IR spectroscopies. Increasing C conte nt degrades the crystalline quality; however, up to y values ranging r oughly from 3% to 5%, depending on sample thickness and used C precurs or, the layers grow epitaxially as revealed by LEED spots, structured Si2p XPD angular scans and RES measurements. The relevant C 1s binding energy, indicative of Si-C bonds, excludes the presence of C-C bonds and no silicon carbide precipitation could be detected. Nevertheless, even in the C-concentration range of good epitaxial growth, neither C 1s XPD polar profiles with Si cubic symmetry, nor marked local vibrati onal mode at 604 cm(-1) in Raman or IR could be detected. These observ ations prove that, at low growth temperature, unexpectedly high amount s of C can be accommodated in a monocrystalline Si lattice via an inco rporation scheme different from the usually invoked substitutional mod e.