Density functional theory calculations of stability and diffusion mechanisms of impurity atoms in Ge crystals

Ge-based substrates are being developed for applications in advanced nano-electronic devices because of their higher intrinsic carrier mobility than Si. The stability and diffusion mechanism of impurity atoms in Ge are not well known in contrast to those of Si. Systematic studies of the stable sites...

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Bibliographic Details
Published in:Journal of applied physics 2014-08, Vol.116 (7)
Main Authors: Maeta, Takahiro, Sueoka, Koji
Format: Article
Language:English
Subjects:
Applied physics
ATOMS
CARRIER MOBILITY
CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
COMPARATIVE EVALUATIONS
CRYSTALS
DENSITY FUNCTIONAL METHOD
Density functional theory
DIFFUSION BARRIERS
Electronic devices
ELECTRONIC EQUIPMENT
Germanium
IMPURITIES
Mathematical analysis
Silicon
STABILITY
SUBSTRATES
TRANSITION ELEMENTS
Transition metals
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Summary:Ge-based substrates are being developed for applications in advanced nano-electronic devices because of their higher intrinsic carrier mobility than Si. The stability and diffusion mechanism of impurity atoms in Ge are not well known in contrast to those of Si. Systematic studies of the stable sites of 2nd to 6th row element impurity atoms in Ge crystal were undertaken with density functional theory (DFT) and compared with those in Si crystal. It was found that most of the impurity atoms in Ge were stable at substitutional sites, while transition metals in Si were stable at interstitial sites and the other impurity atoms in Si were stable at substitutional sites. Furthermore, DFT calculations were carried out to clarify the mechanism responsible for the diffusion of impurity atoms in Ge crystals. The diffusion mechanism for 3d transition metals in Ge was found to be an interstitial-substitutional diffusion mechanism, while in Si this was an interstitial diffusion mechanism. The diffusion barriers in the proposed diffusion mechanisms in Ge and Si were quantitatively verified by comparing them to the experimental values in the literature.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.4893362