Simulation of Vacancy Cluster Formation and Binding Energies in Single Crystal Germanium
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0994-F03-08
Simulation of Vacancy Cluster Formation and Binding Energies in Single Crystal Germanium Piotr Spiewak1,2, Krzysztof Jan Kurzydlowski1, Jan Vanhellemont3, Piotr Wabinski2, Krzysztof Mlynarczyk2, and Igor Romandic4 1 Materials Design Division, Faculty of Materials Science and Engineering, Warsaw University of Technology, Woloska 141, Warsaw, 02-507, Poland 2 Umicore, Ludwiki 4, Warsaw, 01-226, Poland 3 Department of Solid State Sciences, Ghent University, Krijgslaan 281 S1, Ghent, B-9000, Belgium 4 Umicore EOM, Watertorenstraat 33, Olen, B-2250, Belgium
ABSTRACT Results are presented of the simulation of the properties of vacancy clusters in single crystal germanium. Classical molecular dynamics calculations based on a Stillinger and Weber potential were used in a theoretical investigation of different growth patterns of vacancy clusters Vi. The formation and binding energies of vacancy clusters have been studied in the range 1 ≤ i ≤ 35. The energetically favourable growth mode and an estimate of the effective surface energy was determined for a vacancy clusters containing up to 35 vacancies INTRODUCTION The high intrinsic carrier mobility makes germanium-based substrates a possible alternative to conventional silicon substrates for applications in advanced nano-electronic devices. For a successful future application as substrate material, germanium-based substrates will however have to meet the stringent requirements imposed by the International Technology Roadmap for Semiconductors (ITRS). Germanium crystals inherently contain lattice defects that can affect the yield and performance of electronic devices build on Ge substrates. A quantitative understanding of grown-in defect formation in germanium crystals is therefore of crucial importance in order to optimize Ge growth either by crystal pulling or by epitaxy. In this paper results are presented on numerical simulation of the properties of small vacancy clusters in single crystal germanium. In contrast to silicon, the properties of intrinsic point defects in germanium are not at all well known, to a large extent due to a lack of reliable experimental data. Properties of intrinsic point defects were investigated in previous work [1, 2] based on Density Functional Theory (DFT) and classical Molecular Dynamics (MD) simulations of the formation and migration energy of vacancies and self-interstitials, in combination with both experimental and theoretical data available in literature. The properties of small vacancy clusters are difficult to determine experimentally. On the other hand, it is also difficult to study these properties using ab initio and tight-binding atomistic calculations due to large computational demands for these techniques, if a large atomistic domain is used. These limitations can be circumvented by using classical molecular dynamics calculations based on a Stillinger and Weber potential, which are used in the present work for a
theoretical investigation of different possible growth patterns of vacancy agglomerates Vi. The formatio
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