Electronic structure calculations for vacancies and oxygen-related defects in semiconductors

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dc.contributor Aalto-yliopisto fi
dc.contributor Aalto University en
dc.contributor.author Pesola, Marko
dc.date.accessioned 2012-02-10T09:51:28Z
dc.date.available 2012-02-10T09:51:28Z
dc.date.issued 2000-08-18
dc.identifier.isbn 951-22-5102-7
dc.identifier.issn 1455-1802
dc.identifier.uri https://aaltodoc.aalto.fi/handle/123456789/2270
dc.description.abstract Quantum mechanical plane-wave pseudopotential (PWPP) calculations are used to study properties of vacancies and oxygen-related defects in Si and GaAs. Total energies, atomic geometries, charge states, ionization levels, and local vibrational modes for the defects are reported. The convergence of electronic structure calculations with respect to supercell size is studied for the vacancy (V) and divacancy (V2) in Si. The negative-U behaviour has been explored in the case of V in Si. The doubly negative charge state of V is shown to have a split structure which can lead to ionization-enhanced diffusion of V. V2 in Si is shown to have four separate charge states in agreement with experiments. It is found that the neutral (V20) and negative divacancy (V2-) have a mixed structure, including both pairing and resonant-bond characters, V20 being more of the pairing type and V2- more of the resonant-bond type. The ionization levels, microscopic structures and local vibration (LV) modes are calculated for vacancy-oxygen (VO) defects in Si. The ionization level for VO is found near the computational conduction band and the charge-state induced shift in the LV frequency is predicted to be upwards as a function of defect level occupation, in agreement with experiments. VO2 is found to have two degenerate asymmetric stretching modes and thus only one observable mode despite the two oxygen atoms. The LV frequencies for electrically inert oxygen interstitials (Oi) and oxygen dimers (O2i) are presented. The computed asymmetric stretching frequency of the puckered Oi is found to be slightly underestimated compared to the experimental value. Two competing structures for O2i are found: the staggered Oi-Si-Oi conguration and the skewed Oi-Si-Si-Oi conguration. The changes in the LV frequency spectrum with isotopic substitutions of O are calculated, and the experimental frequencies are shown to originate from the staggered form of O2i. The effects of external pressure on structures and vibrational frequencies are reported. Various oxygen chain models for thermal double donors (TDDs) in Si are presented. The first three TDDs (TDD0-TDD2) are found to consist of one four-membered ring where two O atoms are bonded to two common Si atoms with one or two adjacent interstitial O atoms. The following TDDs (TDD3-TDD7) are found to consist of similar rings with flanking Oi atoms. The anomalously fast aggregation of oxygen may be explained by the diffusion of these structures. At the later stages shallow donors with a central "di-Y-lid" core are found to become energetically competitive with the ring structures. An isolated oxygen atom in GaAs is shown to occupy an interstitial Ga-O-As position and to be electrically inactive. The properties of the substitutional off-centered oxygen in arsenic vacancy (OAs) are shown to be at variance with the experimental results. A close similarity of the (AsGa)2-OAs complex with the experimentally observed Ga-O-Ga defect is found. Especially the negative-U and charge-state induced shifts in local vibrational frequencies are in close agreement with the experiments. en
dc.format.extent 34, [49]
dc.format.mimetype application/pdf
dc.language.iso en en
dc.publisher Helsinki University of Technology en
dc.publisher Teknillinen korkeakoulu fi
dc.relation.ispartofseries Dissertations / Laboratory of Physics, Helsinki University of Technology en
dc.relation.ispartofseries 109 en
dc.relation.haspart M. J. Puska, S. Pöykkö, M. Pesola, and R. M. Nieminen, Convergence of supercell calculations for point defects in semiconductors: Vacancy in silicon, Physical Review B, Volume 58, Issue 3, pp. 1318-1325 (1998). [article1.pdf] © 1998 American Physical Society. By permission.
dc.relation.haspart M. Pesola, J. von Boehm, S. Pöykkö and R. M. Nieminen, Spin-density study of the silicon divacancy, Physical Review B, Volume 58, Issue 3, pp. 1106-1109 (1998). [article2.pdf] © 1998 American Physical Society. By permission.
dc.relation.haspart M. Pesola, J. von Boehm, T. Mattila, and R. M. Nieminen, Computational study of interstitial oxygen and vacancy-oxygen complexes in silicon, Physical Review B, Volume 60, Issue 16, pp. 11449-11463 (1999). [article3.pdf] © 1999 American Physical Society. By permission.
dc.relation.haspart M. Pesola, J. von Boehm, and R. M. Nieminen, Vibrations of the Interstitial Oxygen Pairs in Silicon, Physical Review Letters, Volume 82, Issue 20, pp. 4022-4025 (1999). [article4.pdf] © 1999 American Physical Society. By permission.
dc.relation.haspart M. Pesola, Young Joo Lee, J. von Boehm, M. Kaukonen, and R. M. Nieminen, Structures of Thermal Double Donors in Silicon, Physical Review Letters, Volume 84, Issue 23, pp. 5343-5346 (2000). [article5.pdf] © 2000 American Physical Society. By permission.
dc.relation.haspart M. Pesola, J. von Boehm, V. Sammalkorpi, T. Mattila, and R. M. Nieminen, Microscopic structure of oxygen defects in gallium arsenide, Physical Review B, Volume 60, Issue 24, pp. R16267-R16270 (1999). [article6.pdf] © 1999 American Physical Society. By permission.
dc.subject.other Physics en
dc.title Electronic structure calculations for vacancies and oxygen-related defects in semiconductors en
dc.type G5 Artikkeliväitöskirja fi
dc.description.version reviewed en
dc.contributor.department Department of Engineering Physics and Mathematics en
dc.contributor.department Teknillisen fysiikan ja matematiikan osasto fi
dc.subject.keyword density functional theory en
dc.subject.keyword point defect en
dc.subject.keyword thermal donor en
dc.subject.keyword local vibrations en
dc.identifier.urn urn:nbn:fi:tkk-002406
dc.type.dcmitype text en
dc.type.ontasot Väitöskirja (artikkeli) fi
dc.type.ontasot Doctoral dissertation (article-based) en
dc.contributor.lab Laboratory of Physics en
dc.contributor.lab Fysiikan laboratorio fi


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