Growth of partially strain-relaxed Si1-yCy epilayers on (100)Si

1-y

C_y epilayers were grown by MBE on (100) Si single-crystal substrates either directly on a dislocation-free or on a highly dislocated Si buffer layer. The orientation of the epilayers and their strain status were measured by double-crystal X-ray diffraction. Cross sections were prepared for TEM investigations. Epitaxial layers of about 130 nm thickness and carbon contents up to [%at.]1.38 grown on top of dislocation-free 1-μm-thick Si buffer layers were fully strained. In TEM bright field images, no dislocations were found. In order to introduce a high dislocation density in the Si buffer layer, the native oxide on the substrate was only partially removed prior to growing the Si buffer. A Si_1-yC_y film grown on top of that highly dislocated buffer layer showed a partial stress relaxation (a_∥=5.429 Å<a_si=5.431 Å). The large FWHM of transverse rocking scans through the Bragg reflection corresponding to the epilayer indicates a high defect density. TEM cross-section micrographs showed an extension of threading dislocations from the Si buffer layer into the Si_1-yC_y layer.