The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
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Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Engineering Physics and Mathematics, Helsinki University of Technology, for public examination and debate in Auditorium E at Helsinki University of Technology (Espoo, Finland) on the 7th of November, 2003, at 12 o'clock noon.
Overview in PDF format (ISBN 951-22-6770-5) [468 KB]
Dissertation is also available in print (ISBN 951-22-6769-1)
This thesis describes the development, the application and the analysis of the accuracy of state-of-the-art ab initio calculations in the description of intrinsic point defects in technologically important tetrahedrally coordinated isovalent semiconductors.
The calculations presented in this thesis are based on the density-functional theory. The effective single-particle equations derived from the density-functional theory in the Kohn-Sham scheme are solved numerically using the plane-wave basis representation of the valence electrons and the pseudopotential description of the core electrons.
The use of the plane-wave basis enforces periodic boundary conditions. The calculation of the properties of isolated defects within periodic boundary conditions is customarily referred to as the supercell approximation. The supercell method is analyzed in detail in the thesis, with a special emphasis on the calculation of charged point defects.
The developments in the numerical methods presented in this thesis include the implementation of a non-local screened-exchange operator for the improved description of the exchange and correlation energy and a non-uniform charge-compensation scheme for charged point defects in a massively-parallel plane-wave pseudopotential software package.
The included papers present the most accurate numerical electronic structure calculations to date for vacancies in silicon and silicon-germanium, and for interstitials in silicon carbide.
This thesis consists of an overview and of the following 6 publications:
Keywords: electronic structure, density-functional theory, semiconductors, point defects
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© 2003 Helsinki University of Technology