Physica Scripta, T126, 61-64, (2006)

Electronic structure calculations for substitutional copper and monovacancies in silicon

C. D. Latham (a,b,c), M. Ganchenkova (a), R. M. Nieminen (a), S. Nicolaysen (d), M. Alatalo (b), S. Öberg (c) and P. R. Briddon (e)

(a) Laboratory of Physics, Helsinki University of Technology, P.O. Box 1100, FIN-02015 HUT, Finland

(b) Department of Electrical Engineering, Lappeenranta University of Technology, P.O. Box 20, FIN-53851 Lappeenranta, Finland

(c) Department of Mathematics, Luleå University of Technology, SE-97187 Luleå, Sweden

(d) Department of Physics, University of Oslo, P.O. Box 1048 Blindern, N-0316 Oslo, Norway, and Institute for Microsystem Technology, P.O. Box 2243, N-3103 Tonsberg, Norway

(e) Physics Centre, School of Natural Science, University of Newcastle upon Tyne, Newcastle NE1 7RU, UK

(Received 21 August 2005; accepted 26 November 2005; published 17 August 2006)

Abstract

Two different computer program packages based on the self-consistent local-spin-density approximation---AIMPRO and VASP---are employed in this study of substitutional copper Cu_Si and monovacancies V_Si in silicon, including the effects of their charge state.  The programs differ in the types of basis sets and pseudopotentials they use, each with their own relative merits, while being similar in overall quality.  This approach aims to reduce uncertainty in the results, particularly for small or subtle effects, where the risk is greatest that the conclusions are affected by artifacts specific to a particular implementation.  The electronic structures of the two defects are closely related, hence they are expected to behave in a similar manner.  For both defects structural distortions resulting in lower point group symmetries than T_d (the highest possible) are found.  This is in good agreement with the results of previous studies of V_Si.  Much less is known about symmetry-lowering effects for Cu_Si; however, the electronic levels of Cu_Si have been measured accurately, while those for V_Si are less accessible.  Calculating them is a challenging task for theory.  The strategy we adopt, based purely on comparing total energies of supercells in different charge states, with and without model defects, reproduces the three known levels for Cu_Si reasonably well.  Satisfactory results are also obtained for V_Si in so far as can be judged for this more complex case.

DOI: 10.1088/0031-8949/2006/T126/014

PACS: 61.72.Bb, 61.72.Ji, 71.15.Mb

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