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 th e pseudomorphic Si1-x-yGexCy alloys grown on (110) Si and Ge substrates are investigated theoretically with the use of the ab initio pseudopotential m ethod and the virtual-crystal approximation. It is found that the minimum e nergy gaps are all indirect and not monotonically dependent on the composit ions in some cases. In the case of the tensile and compressive strains, the minimum energy gap decreases and increases, respectively, as the C fractio n increases and the Ge fraction is constant. Our result is in good agreemen t with other theoretical results for the Si1-xGex system. (C) 1999 Publishe d by Elsevier Science Ltd. All rights reserved.