Theoretical study of valence-band offsets of strained Si1-x-yGexCy/Si(001) heterostructures

We present a theoretical study of the valence-band offsets (VBOs) of the pseudomorphic Si1-x-yGexCy/Si(001) heterojunctions. Our calculation is based on the ab initio pseudopotential method, the virtual-crystal approximation, and the average-bond-energy theory. It is found that the VBO is sensitive to the strain condition. Initial addition of carbon increases the VBO of the relaxed Si1-x-yGexCy/Si(001) heterostructures. For constant Ge fraction, the VBO decreases and increases with increasing the C fraction in the case of the compressive and tensile strains, respectively. The trends of our results are in agreement with those of other theoretical and experimental results. (C) 1999 American Institute of Physics. [S0021-8979(99)01220-7].