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

Pesola, Marko

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

dc.contributor	Aalto-yliopisto	fi
dc.contributor	Aalto University	en
dc.contributor.author	Pesola, Marko
dc.contributor.department	Department of Engineering Physics and Mathematics	en
dc.contributor.department	Teknillisen fysiikan ja matematiikan osasto	fi
dc.contributor.lab	Laboratory of Physics	en
dc.contributor.lab	Fysiikan laboratorio	fi
dc.date.accessioned	2012-02-10T09:51:28Z
dc.date.available	2012-02-10T09:51:28Z
dc.date.issued	2000-08-18
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.description.version	reviewed	en
dc.format.extent	34, [49]
dc.format.mimetype	application/pdf
dc.identifier.isbn	951-22-5102-7
dc.identifier.issn	1455-1802
dc.identifier.uri	https://aaltodoc.aalto.fi/handle/123456789/2270
dc.identifier.urn	urn:nbn:fi:tkk-002406
dc.language.iso	en	en
dc.publisher	Helsinki University of Technology	en
dc.publisher	Teknillinen korkeakoulu	fi
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.relation.ispartofseries	Dissertations / Laboratory of Physics, Helsinki University of Technology	en
dc.relation.ispartofseries	109	en
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.subject.other	Physics	en
dc.title	Electronic structure calculations for vacancies and oxygen-related defects in semiconductors	en
dc.type	G5 Artikkeliväitöskirja	fi
dc.type.dcmitype	text	en
dc.type.ontasot	Väitöskirja (artikkeli)	fi
dc.type.ontasot	Doctoral dissertation (article-based)	en
local.aalto.digiauth	ask
local.aalto.digifolder	Aalto_76132