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Palladium Related Defects in Silicon Rakesh Dogra Punjab Technical University, INDIA

Palladium Related Defects in Silicon Rakesh Dogra Punjab Technical University, INDIA A.P. Byrne, D.A. Brett, M.C. Ridgway Australian National University, AUSTRALIA. Motivation Fast Diffusion of Pd in Si Introduces Deep Levels in band gap Deep levels act as trap/recombination centres

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Palladium Related Defects in Silicon Rakesh Dogra Punjab Technical University, INDIA

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  1. Palladium Related Defects in Silicon Rakesh Dogra Punjab Technical University, INDIA A.P. Byrne, D.A. Brett, M.C. Ridgway Australian National University, AUSTRALIA

  2. Motivation • Fast Diffusion of Pd in Si • Introduces Deep Levels in band gap • Deep levels act as trap/recombination centres • DLTS: Pd has amphoteric behavior • Acceptor in n-type Si • Donor in p-type Si • Large probability to form Pd-Dopant (P, As, Sb, B) pairs • Pd can be gettered

  3. Motivation Local Structure of isolated Pd and Pd related defects (Pd-dopant, Pd-V, Pd-I pairs) can be studied with Nuclear Hyperfine Methods Perturbed Angular Correlation Spectroscopy

  4. Experimental Details • Sample Preparation • Cz-Si (100) were implanted with Phosphorus and Boron • Doses: 5e15 to 1e20 ions cm-3 • Samples annealed at 900oC for 10s using RTA

  5. 100Pd T1/2=3.6d EC 1+ I = 2+, t1/2 = 214ns, Q = 0.115b, A22 = 0.1 84 keV 2+ 75 keV 1- 100Rh Experimental Details • PAC Probe • 92Zr(12C,4ng)100Pd 100Rh; E = 70 MeV • Recoil energy = 8 MeV • Implantation Depth = 3 mm deep into Si wafers • Isochronal annealing in N2 atmosphere Zr foil 2.5mm 12C Beam Si wafer

  6. Experimental Details • PAC Measurements • Slow-Fast coincident using four conical BaF2 scintillator detectors • Perturbation spectra formed from coincidence counts • Least squares fitted with: • Site 1: Damaged • Site 2: Unperturbed • Site 2: Defect specific • From coupling constant nQ, the largest component of electric field gradient, Vzz is extracted

  7. Results Well defined interaction frequency 5e17 P cm-3 1e18 P cm-3 2e18 P cm-3 5e18 P cm-3 1e19 P cm-3 1e20 P cm-3

  8. Results P-Si Thermally unstable EFG Parameters n-Si ►nQ = 13.1(2) MHz ► h= 0  Symmetric EFG ► EFG orientation <111> p-Si ►nQ = 35.5(3) MHz ► h= 0  Symmetric EFG ► EFG orientation <111>

  9. Pd Si Vacancy Discussions Similar EFG parameters in highly doped n-Si -Same defect formation -Ruled out the formation of Pd-dopant pairs -Defect pair dissociate above TA = 500oC -Maximum probe fraction b/w TA =200-300oC -n+-Si comprises of excess vacancies (negative) -Formation of PdSi-VSi pair, PRB 72 (2005) 193202 -Phosphorus Diffusion Gettering of Pd ! EC EF for n-Si V- Ei Ev=Ec-0.12(2) EV Unique interaction frequency for P dose ≥ 5e17 ions cm-3

  10. <111> IT2 IT1 B IO <100> Discussions • Strong EFG in highly doped p-Si • Defect pair is observed between TA = 550-750oC • Around this temperature Pd diffuses interstitially • Axially symmetric EFG • Tentatively Pdi-BSi pair  supported by theoretical calculations

  11. Discussions Temperature dependence of EFGs Both pairs show T3/2 dependence • Different charge states of the defect complexes • Effect is stronger for Pd-B pair

  12. Acknowledgements • Organizers for waiving off the registration fee • Dept of Science & Technology, India for financial support

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