GROWTH-CONDITIONS FOR COMPLETE SUBSTITUTIONAL CARBON INCORPORATION INTO SI1-YCY LAYERS GROWN BY MOLECULAR-BEAM EPITAXY

To study the conditions for substitutional incorporation of carbon int o Si layers, Lye grew pseudomorphic Si1-yCy/Si superlattices with abso lute carbon concentrations between 0.3% and 2% and growth temperatures varying between 400 and 650 degrees C. We employed a novel technique to derive the amount of substitutional carbon, which is bused on compa rative x-ray rocking analyses of Si1-yCy/Si superlattices grown with c onstant and step-graded temperature profiles. At growth rates around 1 Angstrom/s, we find complete substitutional incorporation of carbon u p to growth temperatures of 550 degrees C and carbon concentrations of about 1%. At higher growth temperatures and/or higher carbon concentr ations, the percentage of substitutional carbon drag significantly, co ncomitant with a thus far unnoticed morphological transition to island growth. (C) 1997 American Institute of Physics. [S0003-6951(97)00652- 9].