Trivacancy in silicon: A combined DLTS and ab-initio modeling study V.P. Markevich a,Ã , A.R. Peaker a , S.B. Lastovskii b , L.I. Murin b , J. Coutinho c , A.V. Markevich c , V.J.B. Torres c , P.R. Briddon d , L. Dobaczewski e , E.V. Monakhov f , B.G. Svensson f a The University of Manchester, Manchester M60 1QD, UK b Scientific-Practical Materials Research Center of NAS of Belarus, Minsk 220072, Belarus c Department of Physics and I3N, University of Aveiro, 3810-193 Aveiro, Portugal d University of Newcastle upon Tyne, Newcastle upon Tyne NE1 7RU, UK e Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw, Poland f Department of Physics, Oslo University, 0316 Oslo, Norway article info Keywords: Silicon Trivacancy Energy levels DLTS Ab-initio modeling abstract Deep level transient spectroscopy and ab-initio modeling have been used for identification of energy levels and structure of trivacancy (V 3 ) in Si. It is found that in the neutral charge state the V 3 is bistable, with the ‘‘fourfold’’ configuration being lower in energy than the (11 0) planar configuration. V 3 in the (110) planar configuration gives rise to two acceptor levels at E c 0.36 eV and E c 0.46 eV in the gap, while in the ‘‘fourfold’’ configuration the defect has trigonal symmetry and an acceptor level at E c 0.075 eV. & 2009 Elsevier B.V. All rights reserved. 1. Introduction It is more than 40 years since electronic structure of fundamental defects in silicon, such as the vacancy and divacancy, were identified [1,2]. Solid experimental results on larger vacancy clusters are very limited. These clusters, however, are keys in controlling many nano-scaling issues in Si. Particularly, they play an important role in capturing unwanted impurities and silicon interstitials so reducing enhanced diffusion of dopants in extremely scaled integrated circuits. Our results represent a step forward in identifying the structure and electronic properties of the trivacancy, which is found to be a bistable center in the neutral charge state with a fourfold coordinated configuration being the energetically favorable one. Among the small V n (nr5) defects, only the divacancy (V 2 ) has been studied extensively experimentally and theoretically [2–7], and its properties are reasonably well understood. The available information on the properties of V 3 , V 4 , and V 5 defects is limited and controversial [8–10]. It is thought that the minimum energy configurations for the neutral V n defects with n from 3 to 5 could be ‘‘part of a hexagonal ring’’ (PHR) configurations [8]. In an electron spin resonance (ESR) study of neutron-irradiated Si the A4, A3, and P1 ESR signals were assigned to such configurations of the V 3 to V 5 defects, respectively [9]. However, it has been argued recently that the fourfold coordinated configurations are lower in energy for the V 3 to V 5 defects than the PHR ones [10]. No clear experimental evidence of the existence of V n clusters in the fourfold coordinated configurations have been presented so far, and electronic properties of the defects in both configurations are not well understood. It is shown in the present work that in the neutral charge state V 3 is bistable, with the fourfold configuration being lower in energy than the (11 0) planar configuration. V 3 in the (11 0) planar configuration gives rise to two acceptor levels at E c 0.36 eV and E c 0.46 eV, while in the fourfold configuration the defect has trigonal symmetry and possess an acceptor level at E c 0.075 eV. 2. Experimental and modeling details Experimental results were obtained by means of DLTS and high-resolution Laplace DLTS (L-DLTS) in combination with uniaxial stress [11].P þ -n diodes for the study were prepared on phosphorus-doped epi-Si (rE30 O cm), which was grown on highly Sb-doped bulk Czochralski-grown Si (Cz-Si) wafers. Oxygen concentration in the epi-layers was close to 4  10 17 cm 3 . Also a few samples from a phosphorus-doped (rE80 O cm) Si float-zone (FZ) ingot with the oxygen content of 1 10 15 cm 3 were studied. For uniaxial stress measurements we used three 1  2  7 mm bars with the long axis oriented in each of the three main crystallographic directions. The bars were cut from a phosphorus- doped (rE20 O cm) Cz-Si crystal. The samples were irradiated with 6 MeV electrons at room temperature and were kept in a ARTICLE IN PRESS Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/physb Physica B 0921-4526/$ - see front matter & 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.physb.2009.08.142 Ã Corresponding author. School of Electrical and Electronic Engineering, University of Manchester, Sackville Str. Building, Manchester M60 1QD, UK. Tel.: +44 1613064647; fax: +44 1613064770. E-mail address: V.Markevich@manchester.ac.uk (V.P. Markevich). Physica B 404 (2009) 4565–4567