Conduction-band-edge variations of pseudomorphic Si1-x-yGexCy alloys on (110) Si and Ge substrates

The trends of the conduction band minima with the alloy compositions for the pseudomorphic Si1-x-yGexCy alloys grown on (110) Si and Ge substrates are investigated theoretically with the use of the ab initio pseudopotential method and the virtual-crystal approximation. It is found that the minimum energy gaps are all indirect and not monotonically dependent on the compositions in some cases. In the case of the tensile and compressive strains, the minimum energy gap decreases and increases, respectively, as the C fraction increases and the Ge fraction is constant. Our result is in good agreement with other theoretical results for the Si1-xGex system. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.