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Lookup NU author(s): Professor Patrick Briddon
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The interstitial carbon impurity (CI) vibrational modes in monocrystalline Si-rich SiGe were investigated by Fourier Transform Infra Red spectroscopy and density functional modelling. The two absorption bands of CI are found to be close to those in silicon, but show shifts in opposite directions with increasing Ge content. The transversal mode band at 932 cm-1 shifts slightly to the high frequency side, while the longitudinal mode at 922 cm-1 suffers a pronounced red-shift. Each CI-related band is found to consist of two components. An annealing of CI in Si1-xGex occures in two stage. During the first stage (210-250 K) the main components of bands anneals and revealed components grow in intensity. At T>250 K all components disappear. Two component structure of bands is suppose most likely correspond to different combinations of Si and Ge atoms in the neighbourhood of the carbon atom. The interstitial carbon defect was modelled by a supercell density-functional pseudopotential method (AIMPRO) for alloys with 4.69% Ge concentration. From energetics, it has been found that each Ge-C bond costs at least 0.4 eV in excess of a Si-C bond. However, structures where Ge atoms are second neighbors to the C atom are marginally bound, and may explain the two-component band structure in the absorption measurements. The vibrational mode frequencies taken from several randomly generated SiGe cells produce the observed opposite shifts for the transverse and longitudinal modes.
Author(s): Khirunenko LI, Pomozov YuV, Sosnin MG, Duvanskii A, Torres VJB, Coutinho J, Jones R, Briddon PR, Abrosimov NV, Riemann H
Editor(s): Cavallini, A; Richter, H; Kittler, M Pizzini, S
Publication type: Conference Proceedings (inc. Abstract)
Publication status: Published
Conference Name: Diffusion and Defect Data Pt.B: Solid State Phenomena. 12th International Autumn Meeting: Gettering and Defect Engineering in Semiconductor Technology, GADEST
Year of Conference: 2008
Publisher: Materials Science and Engineering