Stability of strained Si1−<i>y</i>C<i>y</i> random alloy layers

Abstract

Si1−yCy random alloy material opens up new opportunities for heterostructures based on Si. It offers the possibility of tensile strain within the Si material system without the requirement for relaxed Si1−xGex buffer layers, and when combined with the Si1−xGex system allows some degree of independence between strain and band gap in Si-based semiconductors. Unlike the Si1−xGex system, the Si1−yCy system has a high misfit (52%) and low solubility (&amp;lt;10−6), with a propensity for compound formation. In order to prevent carbide formation, the structures are kinetically stabilized by low-temperature growth. In this work, we consider the metastable critical thickness that can be reached by the Si1−yCy alloys and find it to be considerably less than the comparable thicknesses obtained from Si1−xGex alloys on Si. In the Si1−yCy system, we have found two distinct relaxation regimes for the strained layers. These being low and high mismatch regions where relaxation occurs by the creation of 60° dislocations and microtwins, respectively.