Palladium Related Defects in Silicon Rakesh Dogra Punjab Technical University, INDIA
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Palladium Related Defects in Silicon Rakesh Dogra Punjab Technical University, INDIA A.P. Byrne, D.A. Brett, M.C. Ridgway Australian National University, AUSTRALIA
description
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 - PowerPoint PPT Presentation
Transcript of Palladium Related Defects in Silicon Rakesh Dogra Punjab Technical University, INDIA
Palladium Related Defects in Silicon
Rakesh DograPunjab Technical University, INDIA
A.P. Byrne, D.A. Brett, M.C. RidgwayAustralian National University, AUSTRALIA
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
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
Motivation
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
Experimental Details
PAC Probe• 92Zr(12C,4n)100Pd 100Rh; E = 70 MeV• Recoil energy = 8 MeV• Implantation Depth = 3 m deep into Si wafers• Isochronal annealing in N2 atmosphere 100Pd
1+
2+
1-
I = 2+, t1/2 = 214ns, Q = 0.115b, A22 = 0.1
100Rh
EC T1/2=3.6d
84 keV
75 keV12C Beam Si wafer
Zr foil2.5m
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 Q, the largest component of electric field gradient, Vzz is extracted
(180 , ) (90 , )( ) 2(180 , ) 2 (90 , )C t C tR tC t C t
CtGfAtGAtR i
ii )()()( 22222222
zzQ
eQVh
Experimental Details
Results
0 200 400 600 800
0.00
0.05
0.10
0.00 0.05 0.100
4
0.00
0.05
0.10
0
4
0.00
0.05
0.10
0
4
0.00
0.05
0.10
0
4
0.00
0.05
0.10
0
4
0.00
0.05
0.10
0
4
R(t
)
Time (ns)
5e17 P cm -3
1e18 P cm -3
Inte
nsity
(F
FT
)
2e18 P cm -3
5e18 P cm -3
1e20 P cm-3
1e19 P cm -3
(Grad/s)
Well defined interaction frequency
1E17 1E19 1E210
25
50
Frac
tiona
l Pop
ulat
ion
(%)
Phosphorus concentration (ions/cm2)
1e20 P cm-3
1e19 P cm-3
5e18 P cm-3
2e18 P cm-3
1e18 P cm-3
5e17 P cm-3
0 100 200 300 400 500
0
25
50
75
Rel
ativ
e P
robe
Fra
ctio
n (%
)
Annealing Temperature (C)
0.00
0.08
0.00
0.08
0.00
0.08
0 200 400 600 800
0.00
0.08
0.00
0.08
6.7x1014 P cm-3
5.8x1019 P cm-3
0.7x1019 Sb cm-3
4.3x1019 As cm-3
5.8x1019 P cm-3
<100>
<100>
<100>
<100>
R(t)
Time (ns)
<110>
n-Si ► Q = 13.1(2) MHz► = 0 Symmetric EFG► EFG orientation <111>
p-Si ► Q = 35.5(3) MHz► = 0 Symmetric EFG► EFG orientation <111>
EFG Parameters
0.00
0.08
0.00
0.08
0 200 400 600 800
0.00
0.08
0.00
0.08
<100>
<111>
<100>
<100>1.9x1015 B cm-3
8.4x1019 B cm-3
8.4x1019 B cm-3
5.8x1019 P cm-3R
(t)
Time (ns)
Results
540 600 660 7200
20
40
60
Frac
tiona
l Pop
ulat
ion
(%)
Annealing Temperature (C)
P-Si
Thermally unstable
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 !
Vacancy
Pd
Si
Discussions
EV
EC
EiV-
EF for n-Si
Unique interaction frequency for P dose ≥ 5e17 ions cm-3
Ev=Ec-0.12(2)
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
IT1
IT2
IO
<111>
<100>
B
Discussions
Temperature dependence of EFGsBoth pairs show T3/2 dependence
0 150 300 450 600 75012.0
12.8
13.6
14.4
15.2
20
25
30
35
40
Q (M
Hz)
Q (M
Hz)
Pd-V
Pd-B
Temperature (K)
QPd-V(0)=13.5(2) MHz
Pd-V=6.1E-6 K-3/2
QPd-B(0)=36.8(2) MHz
Pd-B=2e-5 K-3/2
2
31)0()( TT QQ
•Different charge states of the defect complexes
•Effect is stronger for Pd-B pair
Discussions
Acknowledgements
• Organizers for waiving off the registration fee
• Dept of Science & Technology, India for financial support
