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M.G. Ganchenkova 1 , V.A. Borodin 2 , R. Nieminen 1

COSIRES 2004 7th International Conference on Computer Simulation of Radiation Effects in Solids. Annealing of vacancy complexes in P-doped silicon. M.G. Ganchenkova 1 , V.A. Borodin 2 , R. Nieminen 1. 1 COMP/Laboratory of Physics, Helsinki University of Technology, Espoo, Finland

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M.G. Ganchenkova 1 , V.A. Borodin 2 , R. Nieminen 1

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  1. COSIRES 2004 7th International Conference on Computer Simulation of Radiation Effects in Solids Annealing of vacancy complexes in P-doped silicon M.G. Ganchenkova1, V.A. Borodin2, R. Nieminen1 1COMP/Laboratory of Physics, Helsinki University of Technology, Espoo, Finland 2RRC Kurchatov Institute, Moscow, Russia June 2004, Helsinki, Finland

  2. PV and V2 : Experimental data The defects are annealed out DLTS spectra of n-type Si samples after isochronal annealing (30min) between 150 and 300 C 150 C PV V2 250 C Possible reasons: • Recombination with highly mobile interstitial type defect • PV – NO V2 - NO • Thermal dissociation • PV – YES ? V2 – NO ? • Long-range diffusion to sinks • PV – NO ? V2 – YES ? P.Pellegrino et al., Phys.Rev.B, 64 (2001), 195211 June 2004, Helsinki, Finland

  3. P-V complex Schematic representation of E-center • Ps acts as a trap for vacancies … Formation and binding energies for PV complex a. C.S.Nichols, C.G.Van de Walle and S.T.Pantelides, Phys.Rev.B 40, 8 (1989) 5484 b. X.Y.Liu, W.Windle, K.M. Beardmore and M.P.Masqueller, Appl.Phys.Lett 82, 12 (2003), 1839 c. R.Virkunnen and R.M.Nieminen, Comp.Mat.Science 1 (1993) 351 d. R.Car, P.J.Kelly, A.Oshyama, amd S.T.Pantelides, Phys.Rev.Lett. 54, 4 (1985) 360 e. O.Sugino and A.Oshyama, Phys.Rev.B 46 (1992)12335 f. P.M.Fahley, P.B.Griffin, and J.D.Plummer, Rev.Mod.Phys. 61 (1989) 1049 June 2004, Helsinki, Finland

  4. Binding energy vs. constituent separation : PV …with a big vacancy capture radius • PV0, PV- binding energy decreases monotonically with increasing separation • PV is a bound system for P - V separations extending to at least three intermediate chemical bonds June 2004, Helsinki, Finland

  5. 3 NN + 4 NN +… Vacancy jumps : 1 NN + 2 NN 5 NN + … Thermal dissociation or … ??? Experiment : … PV centers anneal already at 150 C … Possible reason:thermal dissociation Dissociation of PV complex - vacancy jumps outside the "three-bond layer" Dissociation of PV complex - multistage process June 2004, Helsinki, Finland

  6. Thermal dissociation or … ??? Activation energy sequence for PV complex dissociation at 150oC : The vacancy return jump is more than 10 times more probable than the jump in the outward direction. favorable conditions for P atom mobility … annealing on sinks ???

  7. L.C.Kimerling: ring mechanism is responsible for annealing of PV centers at 150 C … annealing on sinks ??? Limiting reaction of the ring mechanism – direct exchange jump possible diffusion jumps Migration energies for PV complex a. C.S.Nichols, C.G.Van de Walle and S.T.Pantelides, Phys.Rev.B 40, 8 (1989) 5484 b. X.Y.Liu, W.Windle, K.M. Beardmore and M.P.Masqueller, Appl.Phys.Lett 82, 12 (2003), 1839 June 2004, Helsinki, Finland

  8. Thermal dissociation or … annealing on sinks ??? P atom displacement is rather small, except as a part of PV2- dissociation times are quite small as compared to typical experiment durations: 30 min ! Main reason – Thermal dissociation June 2004, Helsinki, Finland

  9. The relative decrease of PV complex concentration as a function of time and annealing temperature PV+ PV0 PV2- PV-

  10. The relative decrease of PV complex concentration as a function of time and annealing temperature PV2- up to 100 s PV2- up to 1000 s June 2004, Helsinki, Finland

  11. V+ V0 V- V2- V2+ Some words about mono- and divacancy in Si V2+ V20 V2- V22- M.J.Puska et al. Phys. Rev. B 58 (1998) 1318; b) G. D. Watkins, in Deep Centers in Semiconductors, edited by S.T. Pantelides (Gordon and Breach, New York, 1986 ), p.147; c)M.Pesola et al. Phys.Rev. 58 (1998) 1106 ; d)G. D. Watkins, J. W. Corbett, Phys. Rev. 138 (1965) A543; f) P.Hauttojärvi et al. , Defect Diffus.Forum 153-155 (1998) 97; e) E.V. Monakhov, A.Yu. Kuznetsov and B.G. Svensson, Phys. Rev. B 63 (2001) 245322

  12. Binding energy vs. constituent separation : V2 Two vacancies are strongly bound in the first NN configuration The trend of binding energy change with increase of coordination sphere number that defines the mutual arrangement of vacancies in V2 complex the second NN configuration is unstable June 2004, Helsinki, Finland

  13. … vacancy jumps directly to the third or fifth NN position much higher stability of a divacancy as compared to PV June 2004, Helsinki, Finland

  14. The relative decrease of V2 complex concentration as a function of time and annealing temperature V20 V2+ V2- V22-

  15. Conclusions 1 . Both PV complex and a divacancy are strongly bound complexes in silicon, but their kinetic behaviour is completely different. 2. Experimentally observed disappearance of PV signal at temperatures ≈ 150oC can be explained in terms of thermal dissociation of PV complex, but only provided this complex is in the doubly negatively charged state. 3. The divacancy in all investigated charge states is found to be very stable against thermal dissociation at experimentally reported temperatures. 4. Specific features of vacancy interaction at small separations completely exclude any reasonable possibility for divacancy migration in the bound state. June 2004, Helsinki, Finland

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