CCE in irradiated silicon detectors considering the avalanche effect

by

Vladimir Eremin, Elena Verbitskaya, Andrei ZabrodskiiIoffe institute St Petersburg, Russia

Zheng LiBNL

Jaakko HaerconenHIP

CCE in irradiated silicon detectors considering the avalanche effect

RD50 meeting, CERN, 16 – 18 Nov, 2009

Outline

• Model• The effect simulation• CCE(V) profile• CCE(F) profile• Summary

V.Eremin, RD50 Nov.2009

Experimental evidence of the gain

V.Eremin, RD50 Nov.2009

Electric field evolution with fluence in PAD detectors (single

peak model)The electric field in PAD N on P silicon detector

0.0E+00

2.0E+04

4.0E+04

6.0E+04

8.0E+04

1.0E+05

1.2E+05

1.4E+05

1.6E+05

1.8E+05

0.0E+00 5.0E-03 1.0E-02 1.5E-02 2.0E-02 2.5E-02 3.0E-02

Distance, cm

Ele

ctr

ic f

ield

, V

/cm

F=1e14F=3e14F=1E15F=3E15F=1E16

d = 300umV = 500Vg = 1.7e-2 cm-1

V.Eremin, RD50 Nov.2009

Depth profile of multiplication probability

Avalanch probability along the detector thickness

0.0E+00

5.0E+02

1.0E+03

1.5E+03

2.0E+03

2.5E+03

3.0E+03

3.5E+03

0.E+00 2.E-03 4.E-03 6.E-03 8.E-03 1.E-02

Distance, cm

Av

ala

nc

h p

rob

ab

ilit

y,

cm

-1

Electrons, V=1000 V

Holes, V=1000 V

Electrons, V=700 V

Holes, V=700 V

Electric field in detector at different bias voltage

0.0E+00

5.0E+04

1.0E+05

1.5E+05

2.0E+05

2.5E+05

0.E+00 2.E-03 4.E-03 6.E-03 8.E-03 1.E-02

Distance, cm

Ele

ctr

ic f

ield

, V

/cm V=1000 V

V=700 V

g$531,1)

The N on P detector operates at:RT The detector thickness - 300umFluence 1e16 neq/cm2

V.Eremin, RD50 Nov.2009

Voltage dependence of the CCE

CCE(V)

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0 200 400 600 800 1000

Voltage, V

CC

E,

arb

.un

t

The detector operates at RT.The detector thickness is 300um.Fluence 1e16neq/cm2The trapping time: τe= τp= 2.5e-10 s, Electron collection to the n+ side

Calculations are based on trivial SP detector model. What is in a real strip detector ?

V.Eremin, RD50 Nov.2009

Current stabilization and electric field smoothing around strip

E(x)

X

Soft breakdownand hole injection accompanied by trapping

n+ strip

The approach is based on explanation of the high breakdown voltage for the heavily irradiated P on N silicon detectors via the electric field suppression by the local current injection.(V. Eremin et. al., “Scanning Transient Current Study of the I-V Stabilization Phenomenon in Silicon Detectors Irradiated by Fast Neutrons”, NIM A, 388 (1977), 350.)

V.Eremin, RD50 Nov.2009

Extractions from the “Conclusions” of the talk

“The Avalanche Effect in Operation of Heavily Irradiated Si p-i-n Detectors” V. Eremin (Friburg, 2009).

1. The charge multiplication in heavily irradiated detectors is based on two fundamental mechanisms: • the avalanche multiplication in P-N junctions• the electric field manipulation by current injection in the deep level dopped semiconductors.

2. The SPB model conceders a “strong feed-back loop” via the current injection that explains the detector stable operation at the high voltage and the smoothed rise of the collected charge up to 100% of CCE.

V.Eremin, RD50 Nov.2009

PTI model and origin of Double Peak (DP) electric field distribution

V. Eremin, E. Verbitskaya, Z. Li. “The Origin of Double Peak Electric Field Distribution in Heavily Irradiated Silicon Detectors”, NIM A 476 (2002) 556.

trapping

-V

Trapping of free carriers from detector reverse current to midgap energy levels of radiation induced defects leads to DP E(x)

DLs responsible for DP E(x) are midgap DLs:

DD: Ev + 0.48 eV

DA: Ec – 0.52 eV

Neff

V.Eremin, RD50 Nov.2009

Electric field manipulation in bulk of heavily irradiated detector

by hole injection

0 50 100 150 200 2500

5

10

15

20

25

30

p+n

+

T = 140 KV = 210 Volt

Neutron irradiation

Fn = 1.4*1014

cm-2

j, nA/cm2:

0.1 1 5 10 15 20

E, kV

/cm

x, m

V.Eremin, RD50 Nov.2009

E.Verbitskaya et al., “Optimization of electric field distribution by free carriers injection ….” IEEE trans., NS-49 (2002), p. 258.

PTI model of electric field stabilization effect via the

“Soft Avalanche Break Down”

0

2000

4000

6000

8000

10000

12000

0 0.005 0.01 0.015 0.02 0.025 0.03

Distance from p+ contact, cm

Mu

ltip

lica

tio

n p

rob

abil

ity

P+ N+

V.Eremin, RD50 Nov.2009

Calculation of the Electric field with PTI model of “Soft Avalanche

Break Down”DL # Ci-Oi Deep donor V-V Deep acceptorD/A, 0/1 0 0 1 1

electrons holes electrons holes electrons holes electrons holes

Et=Edl-Ev 0.36 0.76 0.48 0.64 0.7 0.42 0.595 0.525sig/e[cm2] 1.00E-15 1.00E-15 1.00E-15 1.00E-15sig/h[cm2] 1.00E-15 1.00E-15 1.00E-15 1.00E-15Ndl[cm-3] 0.00E+00 2.00E+14 0.00E+00 5.00E+15Sig*Vth 1.93E-08 1.47E-08 1.93E-08 1.47E-08 1.93E-08 1.47E-08 1.93E-08 1.47E-08detrap.prob. 8.31E-04 1.42E+04 1.76E-01 6.73E+01 3.23E+03 3.66E-03 2.98E+01 3.97E-01

0

50000

100000

150000

200000

250000

300000

350000

0 0.005 0.01 0.015 0.02 0.025 0.03

Distance from P+ contact, cm

Ele

ctr

ic f

ield

, V

/cm

Fn = 1e16 cm-2, V = 1500, 1000, 700, 500V

0.00E+00

5.00E+05

1.00E+06

1.50E+06

2.00E+06

2.50E+06

0.02 0.022 0.024 0.026 0.028 0.03

Distance from P+ contact, cm

Ele

ctri

c fi

eld

, V/c

m

No SABD With SABD

V.Eremin, RD50 Nov.2009

Voltage dependence of the multiplication effect in detectors

0

200

400

600

800

1000

1200

500 700 900 1100 1300 1500

Voltage, V

Co

llec

ted

ch

arg

e, p

air

s

0

500

1000

1500

2000

2500

3000

3500

4000

500 700 900 1100 1300 1500

Voltage, V

Co

llec

ted

ch

arg

e, p

air

s

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

500 700 900 1100 1300 1500

Voltage, V

Co

llec

ted

ch

arg

e, p

air

s

X=0.028 cm

X=0.029cm

X=0.0295 cm

CCE(V)

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0 200 400 600 800 1000

Voltage, V

CC

E,

arb

.un

t No SABD

Fn = 1e16 cm-2

V.Eremin, RD50 Nov.2009

Fluence dependence of the multiplication effect in detector

0

200

400

600

800

1000

1200

1400

1600

1800

2000

1E+13 1E+14 1E+15 1E+16

Fluence, n/cm-2C

olle

cted

ch

arg

e, p

airs

V = 1000VX = 0.028cm

P+ N+

CCD ~ Vdr*ttr = 10e7*2.5e-10=25umQ gen = 1000 e (10um of MIP track)CCE mip = 30/300*10=1

X

V.Eremin, RD50 Nov.2009

Future

• The set of strip detectors with different width of strips will be finished in 2009.

• Irradiation - spring 2010.• CCE calculation for MIPs with PTI SABD model

V.Eremin, RD50 Nov.2009

Summary

• Earlier predicted phenomenon of stabilization of the maximal electric field at n+ side of heavily irradiated detectors is proofed.

• The soft CCE(V) characteristics of heavily irradiated detectors were successfully modeled.

• The PTI DP model with effective 2 midgap levels for E(X) distribution in irradiated detectors has got new confirmation.

V.Eremin, RD50 Nov.2009