Growth conditions for complete substitutional carbon incorporation into Si1−yCy layers grown by molecular beam epitaxy

Abstract

To study the conditions for substitutional incorporation of carbon into Si layers, we grew pseudomorphic Si1−yCy/Si superlattices with absolute carbon concentrations between 0.3% and 2% and growth temperatures varying between 400 and 650 °C. We employed a novel technique to derive the amount of substitutional carbon, which is based on comparative x-ray rocking analyses of Si1−yCy/Si superlattices grown with constant and step-graded temperature profiles. At growth rates around 1 Å/s, we find complete substitutional incorporation of carbon up to growth temperatures of 550 °C and carbon concentrations of about 1%. At higher growth temperatures and/or higher carbon concentrations, the percentage of substitutional carbon drops significantly, concomitant with a thus far unnoticed morphological transition to island growth.