Theory of carbon-carbon pairs in silicon

R. B. Capaz, A. Dal Pino, , Jr., and J. D. Joannopoulos
Phys. Rev. B 58, 9845 – Published 15 October 1998
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Abstract

Interstitial-substitutional carbon pairs (CiCs) in silicon display interesting metastable behavior associated with two different structural configurations. In this work, we perform extensive ab initio calculations on this system. Our results show the following. (i) The metastable configuration for the neutral charge state displays C1h symmetry and it is reminiscent of the isolated interstitial carbon configuration, i.e., a split interstitial C-Si pair with the substitutional carbon bonded to the silicon interstitial. (ii) The ground-state configuration also has C1h symmetry, but it consists of a single silicon interstitial twofold coordinated in an unusual bridge configuration between two substitutional carbon atoms. With an activation energy of 0.07 eV, this configuration becomes a motional-averaged state with C3v symmetry. (iii) The ground state is lower in energy by 0.11 eV with respect to the metastable state. The jump from one configuration to the other corresponds to a simple “bond-switching” mechanism with a calculated energy barrier of 0.13 eV. (iv) Both configurations have two electronic states in the gap, with gap-state wave functions consistent with the local bonding of the defect complex in each case. (v) Analysis of local-mode vibrations on the ground-state configuration indicates a stronger component in one of the carbon atoms, which explains the experimentally observed isotope splittings. Vibrational frequencies for the metastable configuration are also predicted. All of these results are in satisfactory agreement with experiments.

  • Received 19 March 1998

DOI:https://doi.org/10.1103/PhysRevB.58.9845

©1998 American Physical Society

Authors & Affiliations

R. B. Capaz

  • Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, Rio de Janeiro, RJ 21945-970, Brazil

A. Dal Pino, , Jr.

  • Instituto Tecnológico de Aeronáutica, São José dos Campos, SP 12225, Brazil

J. D. Joannopoulos

  • Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139

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Vol. 58, Iss. 15 — 15 October 1998

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