1

First results on electric field distribution First results on electric field distribution in irradiated epi-Si detectorsin irradiated epi-Si detectors

E. Verbitskaya, V. Eremin, Ioffe Physico-Technical Institute of Russian Academy of Sciences

St. Petersburg, Russia

A. MacchioloMax-Planck-Institut fuer Physik, Munich

11 RD50 Collaboration WorkshopCERN, Geneva, Nov 12-14, 2007

2

1. Background: E(x) distribution in heavily irradiated detectors

2. Approach for simulation of detector Double Peak response and E(x) profile reconstruction with a consideration of electric field

in the “neutral” base

3. Experimental current pulse response in epi-Si SMART detectors irradiated by 1 MeV neutrons and 26 MeV protons and E(x) profiles

4. E(x) profiles in epi-Si detectors reconstructed from current pulse response

Conclusions

E. Verbitskaya et al., 11 RD50 Workshop, CERN, Geneva, Nov 12-14, 2007

OutlineOutline

3

Electric field distribution in heavily irradiated Si detectors

Heavily irradiated detector: Double Junction (DJ) structure:

Z. Li, H. W. Kraner, IEEE TNS 39 (1992) 577

Two depleted regions and a neutral base in-between

D. Menichelli, M. Bruzzi, Z. Li, V. Eremin, NIM A 426 (1999) 135

Two depleted regions and a base in-between with electric field due to potential drop over high resistivity bulk

E. Verbitskaya et al. NIM A 557 (2006) 528-539; “Concept of Double Peak electric field distribution in the development of radiation hard silicon detectors; pres. RESMDD’6, NIM A (in press)

Experimental verification:

A. Castaldini, A. Cavallini, L. Polenta, F. Nava, C. Canali, NIM A476 (2002) 550

E. Verbitskaya et al., 11 RD50 Workshop, CERN, Geneva, Nov 12-14, 2007

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Approach for simulation of detector Double Peak response and E(x) profile reconstruction

with a consideration of electric field in the “neutral” base

Transient current:

Ntr = f(F)

trto ed

EQti /

p+ n+

E1

Eb

E2

W1 Wb W2

h

trthtr Nv

1

Three regions of heavily irradiated detector structure are considered Reverse current flow creates potential difference and electric field in

the neutral base

1) E. Verbitskaya et al. NIM A 557 (2006) 528;2) E. Verbitskaya, Concept of Double Peak electric field distribution in the development of radiation hard silicon detectors; pres. RESMDD’6, NIM A (in press)

Initiated by PTI, developed in:

E. Verbitskaya et al., 11 RD50 Workshop, CERN, Geneva, Nov 12-14, 2007

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i ~ exp(-t/eff)

p+ n+ Signal due to carrier drift in W1 is independent on the properties of Wb and W2

i = i1 ~ exp(-t/tr)

W1, Neff1, E1

tcol

tcol: depends on Eb and Wb Eb, Wb

Charge collected inside W2

QW2

QW2 = Qo(d – W1 –Wn)/d Wb, W2, E2, Neff2

Edx = V

Simulation of detector Double Peak response and E(x) profile reconstruction

with a consideration of electric field in the “neutral” base

E. Verbitskaya et al., 11 RD50 Workshop, CERN, Geneva, Nov 12-14, 2007

6

New development of E(x) profile reconstruction with a consideration of electric field in the “neutral” base

Current pulse response is considered as drift current

i(t) = enE(x)

Correction for carrier trapping is done

trcorr ttiti /exp)()(

r is parameter dependent on fluence

Edx = V at x = d

E. Verbitskaya et al., 11 RD50 Workshop, CERN, Geneva, Nov 12-14, 2007

Special algorithm and software are developed which give direct calculation of the electric field distribution

7

Current pulse response in irradiated epi-Si SMART detectors

Detectors: SMART, p+ - n-epi Si - n+ wafer

Experimental Technique: TCT setup at Ioffe Institute TCT setup response 0.8 ns Temperature range 77 – 373K Laser wavelength 830 m

All experiments: Laser at p+ side: electron collection

E. Verbitskaya et al., 11 RD50 Workshop, CERN, Geneva, Nov 12-14, 2007

Epi-layer thickness: 150 m

# irradiation equiv. fluence (cm-2)T time (min)

W12 SMG22 26 MeV protons 7.00E+14 80C 60

W13 SMG 15 1 Mev Neutrons 8.50E+14

W12 SMG 15 1 Mev Neutrons 8.50E+14 80C 60

annealing

no annealing

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Current pulse response in proton irradiated epi-Si SMART detectors

E. Verbitskaya et al., 11 RD50 Workshop, CERN, Geneva, Nov 12-14, 2007

SMART W12 SMG22, epi-Si, 26 MeV protons, Fp = 7e14 cm-2, p+ side

-0.002

0

0.002

0.004

0.006

0.008

0.01

0.012

0.0E+00 2.0E-09 4.0E-09 6.0E-09 8.0E-09 1.0E-08 1.2E-08 1.4E-08 1.6E-08

time (s)

sig

na

l (V

olt

)7.1 V

7.9 V

9.6 V

11.9 V

14.4 V

16.9 V

21 V

25.4 V

29.9 V

36.5 V

44.1 V

53.8 V

64.5 V

78.2 V

93 V

111.7 V

133.3 V

158.9 V

189.5 V

Room temperature

9

Current pulse response in proton irradiated epi-Si SMART detectorsSMART W12 SMG22 epi-Si, 26 MeV protons, Fp = 7e14 cm-2, p+ side

0.008

0.0085

0.009

0.0095

0.01

0.0E+00 2.0E-09 4.0E-09 6.0E-09 8.0E-09 1.0E-08 1.2E-08 1.4E-08 1.6E-08time (s)

sig

na

l (V

olt

)19 V

30 V

40 V

51 V

61 V

71.8 V

81.8 V

92.8 V

103.9 V

113.8 V

124.8 V

134.9 V

145.8 V

155.8 V

166.8 V

176.8 V

187.7 V

198.7 V

-10 C

E. Verbitskaya et al., 11 RD50 Workshop, CERN, Geneva, Nov 12-14, 2007

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Current pulse response in proton irradiated epi-Si SMART detectors

Full depletion at -10C occurs at higher V

W12 SMG22, 26 MeV, Fp = 7e14 cm-2, RT

-0.001

0

0.001

0.002

0.003

0.004

0.005

0.006

0.007

0.008

0 2 4 6 8 10 12 14 16

time (ns)

sig

na

l (V

)

29.9 V

36.5 V

44.1 V

53.8 V

78.2 V

W12 SMG22, 26 MeV, Fp = 7e14 cm-2, -10C

0.008

0.0085

0.009

0.0095

0 2 4 6 8 10 12 14 16time (ns)

sig

nal

(V

)

71.8 V

81.8 V

92.8 V

103.9 V

113.8 V

26 MeV protons, Fp = 7e14 cm-2

E. Verbitskaya et al., 11 RD50 Workshop, CERN, Geneva, Nov 12-14, 2007

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E(x) and Neff(x) profiles in proton irradiated epi-Si detectors

Neff(x), W12 SMG22

-8E+12

-6E+12

-4E+12

-2E+12

0

2E+12

4E+12

6E+12

8E+12

0 0.005 0.01 0.015

x (cm)

Nef

f (c

m-3

)

29.9 V36.6 V44.1 V53.8 V78.2 V

E(x), W12 SMG22

0

2000

4000

6000

8000

10000

0 0.005 0.01 0.015x (cm)

E (

V/c

m)

29.9 V

36.6 V

44.1 V

53.8 V

78.2 V

Room temperature

RTE (x) epi-Si W12 SMG22. T = -10C

0

2000

4000

6000

8000

10000

12000

14000

0 0.005 0.01 0.015x (cm)

E (

V/c

m)

71.8 V

81.8 V

92.8 V

103.9 V

113.8 V

T = -10C

Neff(x)

-1.5E+13

-1E+13

-5E+12

0

5E+12

1E+13

1.5E+13

0 0.005 0.01 0.015

x (cm)

Nef

f (c

m-3

)

71.8 V

81.8 V

92.8 V

103.9 V

113.8 V

E. Verbitskaya et al., 11 RD50 Workshop, CERN, Geneva, Nov 12-14, 2007

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E(x) and Neff(x) profiles: comparison at different temperatures

E(x), W12 SMG22

0

2000

4000

6000

8000

10000

0 0.005 0.01 0.015x (cm)

E (

V/c

m)

RT, 78 V

-10C, 82 V

E. Verbitskaya et al., 11 RD50 Workshop, CERN, Geneva, Nov 12-14, 2007

E(x), W12 SMG22

-1.5E+13

-1E+13

-5E+12

0

5E+12

1E+13

1.5E+13

0 0.005 0.01 0.015

x (cm)

Ne

ff (

cm

-3)

RT, 78 V

-10 C, 82 V

Base region exists near the p+ contact:

RT: V≤40 V -10C: V≤80 V

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Current pulse response in neutron irradiated epi-Si SMART detectors

E. Verbitskaya et al., 11 RD50 Workshop, CERN, Geneva, Nov 12-14, 2007

W13 SMG15

-0.0005

0

0.0005

0.001

0.0015

0.002

0.0025

0.003

0.0035

0.004

2 4 6 8 10 12 14

time (ns)

sig

na

l (V

)

18.1 V

21.1 V

38.7 V

56.7 V

74 V

92.2 V

110 V

126.5 V

143.3 V

159.4 V

173.3 V

186.3 V

197.3 V

214.2 V

203.3 V

196.1 V

181.3 V

166 V

152 V

as-irradiated

Reverse current is significant at V>200 V

W13 SMG15, Fn = 8.51014 cm-2, as-irradiated

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Current pulse response in neutron irradiated epi-Si SMART detectors

E. Verbitskaya et al., 11 RD50 Workshop, CERN, Geneva, Nov 12-14, 2007

W12 SMG15

0

0.001

0.002

0.003

0.004

0.005

0.006

0.007

2 4 6 8 10 12 14

time (ns)

sig

nal

(V

)

6.8 V

24.3 V

44.1 V

64.6 V

84.5 V

105.6 V

126.8 V

147 V

168.4 V

189.9 V

211 V

232.4 V

253.3 V

274.6 V

294.7 V

315.7 V

334.5 V

355.2 V

376.6 V

annealing 80C, 60 min

W12 SMG15, Fn = 8.51014 cm-2, annealed 80C, 60 min

15

Current pulse response in neutron irradiated epi-Si detectors

0.00E+00

1.00E-03

2.00E-03

3.00E-03

4.00E-03

5.00E-03

6.00E-03

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

84.5 V

105.6 V

126.8 V

147.1 V

189.9 V

W12 SMG 15annealing 80C, 60 min

SMART W13 SMG15 epi-Si, 1 MeV neutrons, Fn = 8.5e14 cm-2

-0.001

0

0.001

0.002

0.003

0.004

0 2 4 6 8 10 12 14 16

time (ns)

sig

nal

(V

)

21.1 V

38.7 V

74 V

92.2 V

143.3 V

173.3 V

186.3 V

I-V characteristics

0

200

400

600

800

1000

1200

0 50 100 150 200 250 300 350 400

bias voltage (V)

reve

rse

curr

ent

(uA

)

W13 SMG15, as-irradiated

W12 SMG15, 80C, 60min

Annealing results in significant reduction of current.

Increase of electric field near the interface wafer-epi-layer due to carrier trapping from enhanced current at higher V?

E. Verbitskaya et al., 11 RD50 Workshop, CERN

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E(x) and Neff(x) profiles in neutron irradiated epi-Si detectors

E(x)

0

5000

10000

15000

20000

25000

30000

35000

0 0.002 0.004 0.006 0.008 0.01 0.012 0.014x (cm)

E (

V/c

m)

84.5 V

105.6 V

126.8 V

147.1 V

189.9 V

W12 SMG 15annealing 80C, 60 min

Neff(x)

-2.5E+13

-2E+13

-1.5E+13

-1E+13

-5E+12

0

5E+12

1E+13

1.5E+13

2E+13

2.5E+13

0 0.005 0.01 0.015

x (cm)

Ne

ff (

cm

-3)

84.5 V

105.6 V

126.8 V

147.1 V

189.9 V

W12 SMG 15annealing 80C, 60 min

W13 SMG15, E(x)

0.0E+00

5.0E+03

1.0E+04

1.5E+04

2.0E+04

2.5E+04

3.0E+04

3.5E+04

4.0E+04

0 0.005 0.01 0.015x (cm)

E (

V/c

m)

109.9 V

126.5 V

143.3 V

173.3 V

186.8 V

W13 SMG 15as-irradiated

W13 SMG15, Neff(x)

-6E+13

-4E+13

-2E+13

0

2E+13

4E+13

6E+13

8E+13

0 0.005 0.01 0.015

x (cm)

Nef

f (c

m-3

)

109.9 V

126.5 V

143.3 V

173.2 V

186.8 V

W13 SMG 15as-irradiated

W13 SMG15, as-irradiated W12 SMG15, anneal 80C, 60 min

E. Verbitskaya et al., 11 RD50 Workshop, CERN, Geneva, Nov 12-14, 2007

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E(x) and Neff(x) profiles: comparison of as-irradiated and annealed detectors

E(x)

0.0E+00

5.0E+03

1.0E+04

1.5E+04

2.0E+04

2.5E+04

3.0E+04

3.5E+04

4.0E+04

0 0.005 0.01 0.015x (cm)

E (

V/c

m)

143 V

187 V

147 V

190 V

no anneal

80C, 60 min

Neff(x)

-5.0E+13

-4.0E+13

-3.0E+13

-2.0E+13

-1.0E+13

0.0E+00

1.0E+13

2.0E+13

3.0E+13

0 0.005 0.01 0.015

x (cm)

Ne

ff (

cm

-3)

143 V

187 V

147 V

190 V

no anneal

80C, 60 min

E(x) Neff(x)

E at n+ contact is higher in as-irradiated detector

Low field base region near p+ contact exists in both detectors, annealing doesn’t eliminate it

E. Verbitskaya et al., 11 RD50 Workshop, CERN, Geneva, Nov 12-14, 2007

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Trapping time constants

Proton irradiated, 71014 cm-2: 1.6-1.8 ns

Neutron irradiated, 8.51014 cm-2:

1.1 ns – as-irradiated 1.4 ns - annealed

E. Verbitskaya et al., 11 RD50 Workshop, CERN, Geneva, Nov 12-14, 2007

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Conclusions

SCSI occurs in epi-Si detectors irradiated by 26 MeV protons and 1 MeV neutrons (F = (7-8)1014 cm-

2).

DP response in epi-Si irradiated detectors is related with base region rather than with DP E(x). Electric field in the base regions arises from current flow and potential drop over the base.

Base region with rather high E (~few kV/cm) extends near the surface pf the epi-layer.

As-irradiated detector – enhanced current and increase of electric field related to trapping at the n+ contact? – needs additional study.

New method of E(x) reconstruction in irradiated Si detectors is universal and is related to minimal number of parameters.

E. Verbitskaya et al., 11 RD50 Workshop, CERN, Geneva, Nov 12-14, 2007

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Acknowledgements

This work was supported in part by:

• Grant of the President of RF SSc-5920.2006.2• INTAS-CERN project # 03-52-5744

Thank you for your attention!

Acknowledgemets to SMART team - M. Boscardin, M. Bruzzi, D. Creanza, D. Menichelli, C. Piemonte.