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Energy Differences Between the Si and the Ge Dangling Bond Defects in a-Si1-xGex Alloys

Published online by Cambridge University Press:  21 February 2011

S.M. Cho ,
B.N. Davidson  and
G. Lucovsky
S.M. Cho
Affiliation:
Department of Physics, and Materials Science and Engineering, North Carolina State University, Raleigh, N.C. 27695–8202
B.N. Davidson
Affiliation:
Department of Physics, and Materials Science and Engineering, North Carolina State University, Raleigh, N.C. 27695–8202
G. Lucovsky
Affiliation:
Department of Physics, and Materials Science and Engineering, North Carolina State University, Raleigh, N.C. 27695–8202
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Abstract

We have investigated the difference in the electronic energies of neutral Si and Ge dangling bond states in undoped a-Si1-xGex alloys as a function of the alloy composition, x, and local bond-angle distortions. The local density of states, LDOS, in a-Si1-xGex alloys has been calculated using nearest-neighbor interactions, and employing the Cluster Bethe Lattice method. We conclude that for ideal, tetrahedrally bonded amorphous semiconductors alloys, the Ge dangling bond energy is lower than that of Si dangling bonds by ∼ 0.13 eV, independent of the specific nearest neighbors to the dangling bond (3 Si-atoms, 2 Si-atoms and 1 Ge-atom, etc.), but that the spread in dangling bond energies associated bond-angle variations of the order of 6–8 degrees can be larger than this energy difference (∼0.3 eV or greater). This means that structural disorder, rather than chemical disorder causes Si and Ge-atom dangling bond states to overlap in their energy distributions.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 258: Symposium A – Amorphous Silicon Technology – 1992 , 1992 , 583
Copyright
Copyright © Materials Research Society 1992

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References

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