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Electric field distribution in irradiated MCZ Si detectors. E. Verbitskaya , V. Eremin, I. Ilyashenko Ioffe Physico-Technical Institute of Russian Academy of Sciences St. Petersburg, Russia Z. Li Brookhaven National Laboratory, Upton, NY, USA J. Härkönen - PowerPoint PPT Presentation
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1
Electric field distribution Electric field distribution in irradiated MCZ Si detectorsin irradiated MCZ Si detectors
E. Verbitskaya, V. Eremin, I. IlyashenkoIoffe Physico-Technical Institute of Russian Academy of Sciences
St. Petersburg, Russia
Z. LiBrookhaven National Laboratory, Upton, NY, USA
J. Härkönen Helsinki Institute of Physics, CERN/PH, Geneva, Switzerland
Marko Mikuž, Vladimir CindroJožef Stefan Institute, Ljubljana
Chris ParkesGlasgow University
9 RD50 Collaboration WorkshopCERN, Geneva, Oct 16-18, 2006
2
OutlineOutline
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. Comparison of experimental results on DP pulse response of MCZ Si detectors irradiated by 1 MeV neutrons and 24 GeV protons with F > 1014 cm-2 (detectors developed under “Technotest” sub-project)
4. Simulation of DP E(x) profile with a consideration of carrier trapping to midgap energy levels
5. Reconstruction of E(x) profiles in MCZ Si detectors
Conclusions
E. Verbitskaya et al., 9 RD50 Workshop, CERN, Geneva, Oct 16-18, 2006
3
Models for electric field distribution in irradiated Si detectors
Standard model
Neff = const, E(x) – linear, Vfd derived from C-V curves
Valid for F 5·1013 cm-2
p+ n+
-Neff
p+ n+
-Neff
n-type Sibeyond SCSI
-Neff
E. Verbitskaya et al., 9 RD50 Workshop, CERN, Geneva, Oct 16-18, 2006
4
Models for electric field distribution in heavily irradiated Si detectors
Detector: Double Junction structure:
Two depleted regions at the sides of detectors irradiated beyond SCSI, peaks of E at p+ and n+ contacts
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. Operation of heavily irradiated silicon detectors in non- depletion mode. Pres. RESMDD’05, Nucl. Instr. and Meth. A 557 (2006) 528-539
p+ n+
V2
V1
pinch
-off
V>Vfd
Wb
p+ n+
V2
V1
pinch
-off
V>Vfd
Wb
Bulk Si: n-type converts to high resistivity p-type E. Borchi, M. Bruzzi et al, IEEE Trans. Nucl. Sci. 46 (1999) 834; M. Bruzzi, IEEE Trans. Nucl. Sci. 48 (2001) 960.
E. Verbitskaya et al., 9 RD50 Workshop, CERN, Geneva, Oct 16-18, 2006
5
Experimental evidence of Double Peak electric field distribution
Measurements of OBIC and surface potential in non-irradiated and irradiated detectors
Existence of two depletion layers adjacent to the contacts and separated by a layer inverted to p-type Si (close to intrinsic)
Insignificant difference in E(x) near the p+ contact in non-irradiated and irradiated Si detectors
Model of DP E(x) distribution: ionization of DLs due to band bending near the contacts
A. Castaldini, A. Cavallini, L. Polenta, F. Nava, C Canali, NIM A476 (2002) 550
E. Verbitskaya et al., 9 RD50 Workshop, CERN, Geneva, Oct 16-18, 2006
6
Origin of Double Peak (DP) electric field distribution
V. Eremin, E. Verbitskaya, Z. Li. NIM A 476 (2002) 556
Trapping of free carriers from detector reverse current to Deep Levels leads to DP E(x)
trapping
-V
midgap DLs:
DD: Ev + 0.48 eV
DA: Ec – 0.52 eV
E. Verbitskaya et al., 9 RD50 Workshop, CERN, Geneva, Oct 16-18, 2006
7
Approach for pulse response simulation and E(x) reconstruction with a consideration of electric field in the base
Transient current:
eff
odr Ne
Neff, Ntr = f(F)
effto ed
EQti /
p+ n+
E1
Eb
E2
W1 Wb W2
h
111 trdreff
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
Goal: reconstruction of electric field profile from current pulse response, simulation of detector DP pulse response
E. Verbitskaya et al. Pres. RESMDD’05, NIM A 557 (2006) 528-539
E. Verbitskaya et al., 9 RD50 Workshop, CERN, Geneva, Oct 16-18, 2006
8
i ~ exp(-t/eff)
p+ n+
Simulation of pulse response for carrier generation from one side of detector
Signal due to carrier drift in W1 is independent on the properties of Wb and W2
i = i1 ~ exp(-t/eff)
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
E. Verbitskaya et al., 9 RD50 Workshop, CERN, Geneva, Oct 16-18, 2006
9
Experimental tool for study of electric field distribution
Transient Current Technique
Pulse Laser for generation of nonequilibrium carriers
Short wavelength of laser (e or h generation from one side and transport through detector bulk)
E. Verbitskaya et al., 9 RD50 Workshop, CERN, Geneva, Oct 16-18, 2006
10
Experimental observations of DP current pulse response
-2.0E-05
0.0E+00
2.0E-05
4.0E-05
6.0E-05
8.0E-05
1.0E-04
1.2E-04
1.4E-04
1.6E-04
0 5 10 15 20 25 30
time (ns)
curr
ent
(A)
Ряд1
Ряд2
Ряд3
Ряд4
Ряд5
Ряд6
Ряд7
Ряд8
Ряд9
Ряд10
Ряд11
Ряд12
Ряд13
Ряд14
Ряд15
Ряд16
Ряд17
Ряд18
Ряд19
NeutronPti_cz_d11Fn = 5e14 cm-2before anneal p+ side, RT
-1.0E-05
0.0E+00
1.0E-05
2.0E-05
3.0E-05
4.0E-05
5.0E-05
6.0E-05
7.0E-05
8.0E-05
9.0E-05
1.0E-04
0 5 10 15 20 25 30
time (ns)
curr
ent
(A)
Ряд1
Ряд2
Ряд3
Ряд4
Ряд5
Ряд6
Ряд7
Ряд8
Ряд9
Ряд10
Ряд11
Ряд12
Ряд13
Ряд14
Ряд15
Ряд16
Ряд17
Ряд18
Ряд19
NeutronPti_cz_d115e14n+ side, RT
• Electron collection (p+ side): second peak (H2) increases with V: H1/H2 • Major junction at n+ side: SCSI:
1. 1 MeV neutron irradiation MCZ Si, Fn = 51014 cm-2
E. Verbitskaya et al., 9 RD50 Workshop, CERN, Geneva, Oct 16-18, 2006
11
2. 24 GeV proton irradiation MCZ n-Si, Fp = 11015 cm-2
0.0E+00
5.0E-05
1.0E-04
1.5E-04
2.0E-04
2.5E-04
3.0E-04
0 5 10 15 20 25 30time (ns)
cu
rre
nt
(A)
36 V
76 V
120 V
205 V
246 V
303 V
322 V
350 V
protons 1e15cm-2PTI_CZ-e4p+ side
0.0E+00
5.0E-05
1.0E-04
1.5E-04
2.0E-04
2.5E-04
3.0E-04
0 5 10 15 20 25 30time (ns)
curr
ent
(A)
42 V
88 V
134 V
205 V
250 V
294 V
357 V
395 V
417 V
protons 1e15cm-2BNL_114p+ side
0.0E+00
5.0E-05
1.0E-04
1.5E-04
2.0E-04
2.5E-04
3.0E-04
0 5 10 15 20 25 30time (ns)
curr
ent
(A)
40 V
75 V
120 V
205 V
245 V
303 V
322 V
350 V
protons 1e15cm-2HIP_62p+ side
Influence of processing:difference in H1/H2
Double Peak for all detectorsat V > 200 V1st peak dominates (H1/H2>1)
E. Verbitskaya et al., 9 RD50 Workshop, CERN, Geneva, Oct 16-18, 2006
12
DP response under long term annealing MCZ Si, Fp = 11015 cm-2
-5.0E-06
0.0E+00
5.0E-06
1.0E-05
1.5E-05
2.0E-05
2.5E-05
3.0E-05
0 5 10 15 20
time, ns
curr
ent,
A
Series1
Series2
Series3
Series4
Series5
Series6
Series7
Series8
Series9
Series10
Series11
Series12
Series13
Series14
Series15
Series16
Series17
Series18
Series19
Proton, 1e15 cm-2Pti_cz_e4
p+ sidebefore anneal
-5.0E-06
0.0E+00
5.0E-06
1.0E-05
1.5E-05
2.0E-05
2.5E-05
0 5 10 15 20
time, nscu
rren
t, A
Series1
Series2
Series3
Series4
Series5
Series6
Series7
Series8
Series9
Series10
Series11
Series12
Series13
Series14
Series15
Series16
Series17
Series18
Series19
proton, 1e15 cm-2PTI-CZ-e42 anneal, 25 min, t_sum = 35 min
-5.0E-06
0.0E+00
5.0E-06
1.0E-05
1.5E-05
2.0E-05
2.5E-05
0 5 10 15 20
time, ns
curr
ent,
A
Series1
Series2
Series3
Series4
Series5
Series6
Series7
Series8
Series9
Series10
Series11
Series12
Series13
Series14
Series15
Series16
Series17
Series18
Series19
proton, 1e15 cm-2PTI-CZ-e43 anneal, 50 min, t_sum = 85 min
-1.0E-05
0.0E+00
1.0E-05
2.0E-05
3.0E-05
4.0E-05
5.0E-05
6.0E-05
7.0E-05
8.0E-05
9.0E-05
0 5 10 15 20
time (ns)
curr
ent
(A)
Series1
Series2
Series3
Series4
Series5
Series6
Series7
Series8
Series9
Series10
Series11
Series12
Series13
Series14
Series15
Series16
Series17
Series18
Series19
Proton, 1e15 cm-2Pti_cz_e45 anneal, 180 min, t_sum = 355 min
-2.0E-05
0.0E+00
2.0E-05
4.0E-05
6.0E-05
8.0E-05
1.0E-04
0 5 10 15 20
time (ns)
curr
ent
(A)
Series1
Series2
Series3
Series4
Series5
Series6
Series7
Series8
Series9
Series10
Series11
Series12
Series13
Series14
Series15
Series16
Series17
Series18
Series19
Proton, 1e15 cm-2Pti_cz_e46 anneal, 6 h t_sum = 715 min
-1.0E-05
0.0E+00
1.0E-05
2.0E-05
3.0E-05
4.0E-05
5.0E-05
6.0E-05
7.0E-05
8.0E-05
9.0E-05
2 7 12 17 22
time (ns)
curr
ent
(A)
Series1
Series2
Series3
Series4
Series5
Series6
Series7
Series8
Series9
Series10
Series11
Series12
Series13
Series14
Series15
Series16
Series17
Series18
Series19
Proton, 1e15 cm-2Pti_cz_e47 anneal, 6 ht_sum = 1075 min
Before anneal 2: 35 min (total tann)
Tann = 80C, 7 steps
3: ~1.5 h
5: 6 h 6: 12 h 7: 18 h
V = 40-440 V
PTI-CZ-e4
• H1 and H2 rise at each step• H1/H2 changes under annealing and 1
E. Verbitskaya et al., 9 RD50 Workshop, CERN, Geneva, Oct 16-18, 2006
13
Evolution of Double Peak response under annealing,MCZ Si, Fp = 11015 cm-2
Annealing of DP response
0
0.2
0.4
0.6
0.8
1
1.2
0 5 10 15 20time (ns)
cu
rre
nt
no
rma
lize
d
0
10
35
85
175
355
715
1075
t_ann (min):BNL-114Fp = 1e15 cm-2V = 420 V
Normalized response
Annealing of DP response
0
0.2
0.4
0.6
0.8
1
1.2
0 5 10 15 20 25 30time (ns)
curr
ent
no
rmal
ized
0
1: 10
2: 35
3: 85
4: 175
5: 355
6: 715
7: 1075
t_ann (min):
PTI_cz_e4Fp = 1e15 cm-2V = 300 V
eff doesn’t change under annealing
E. Verbitskaya et al., 9 RD50 Workshop, CERN, Geneva, Oct 16-18, 2006
14
Amplitude ratio H1/H2 under annealingMCZ Si, Fp = 11015 cm-2
Annealing of DP response; Fp = 1e15 cm-2
0
1
2
3
4
5
6
0 200 400 600 800 1000 1200t_ann (min)
H1
/H2
PTI-CZ-e4, 300 V
BNL-CZ-114, 420 V
Stages of DP shape non-monotonous changes: 1. increase of H1
2. increase of H2
shape tends to single peak (E(x) linear) at tann = 1.5-6 h3. reduction of H2 and increase of pulse width
E. Verbitskaya et al., 9 RD50 Workshop, CERN, Geneva, Oct 16-18, 2006
15
Comparison between n and p: amplitude ratio H1/H2 in DP response
0
5
10
15
20
25
0 100 200 300 400 500 600V (Volt)
H1/
H2
PTI-CZ-e4
BNL-CZ-114
PTI-CZ-d11
BNL-CZ-98
p
n
≤1
Fluence:Fn = 51014 cm-2
Fp = 11015 cm-2
E. Verbitskaya et al., 9 RD50 Workshop, CERN, Geneva, Oct 16-18, 2006
16
Fn = 5e13 cm-2, PTI-Cz-c12, n+ side, RT
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
0 100 200 300 400 500 600 700 800 900 1000V (Volt)
Q_n
orm
before anneal
6 min
16 min
36 min
76 min
PTI-Cz-d11, RT
0
0.2
0.4
0.6
0.8
1
1.2
0 200 400 600 800 1000V (Volt)
Q_n
orm
Q_total
Q(20 ns)
Q(10 ns)
Q_total
Q (20 ns)
Q(10 ns)
before anneal
156 min
5e14 cm-2
neutrons Q normalized total, Fp = 1e14 cm-2, before anneal
0
0.2
0.4
0.6
0.8
1
1.2
0 100 200 300 400 500 600
V (Volt)
Q n
orm
aliz
ed PTI_cz-d3BNL_101HIP_21PTI_FZ_b3
protons
Q normalized total, Fp = 1e15 cm-2, before anneal
0
0.2
0.4
0.6
0.8
1
1.2
0 100 200 300 400 500V (Volt)
Q n
orm
iliz
ed
PTI_cz-e4
BNL_114
HIP_62
# BNL-114, Fp = 1e15 cm-2, anneal 1075 min
0
0.2
0.4
0.6
0.8
1
0 100 200 300 400 500
V (Volt)
Q n
orm
aliz
ed
Q total
Q(20 ns)
Q(10 ns)
Comparison: MCZ Si, Q(V)
Single peak
Double peak
1e15 cm-2
5e13 cm-21e14 cm-2
annealing
17
for neutrons and protons, TCT data
FZ, n: 0.022
MCZ, n: 0.017MCZ, p: 0.0045 Z. Li et al. Radiation hardness of high
resistivity magnetic Czochralski silicon detectors after gamma, neutron,
and proton radiations, TNS- 51 (2004) 1901-1908
Experimental data on Neff(F) and Vfd dependence in MCZ Si detectors
0
50
100
150
200
250
300
1.0E+13 1.0E+14 1.0E+15
24 GeV/c Proton Fluence [p/cm2]
Vfd
[V
]
V_dep(QVe) V_dep(QVh)
A. Bates and M. Moll. A comparison between irradiated Magnetic Czochralski and Float Zone silicon detectors using the Transient Current Technique. NIM A 555 (2005) 113
Depletion voltage has passed its minimum value without type inversion
E. Verbitskaya et al., 9 RD50 Workshop, CERN, Geneva, Oct 16-18, 2006
18
E(x) profile in MCZ Si detectors irradiated by 24 GeV protons (earlier results)
Pulse response fit and E(x) reconstruction basing on three region structure Fp = 2.21015 cm-2 Electron collection (p+ side) SMART detector
M. Scaringella et al. Localized energy levels generated in Magnetic Czochralski silicon by proton irradiation and their influence on the sign of space charge density. NIM A, in press; and N. Manna, pres. 8 RD50 Workshop, June 25-28, 2006, Prague
Wide region with positive space charge!
“Puzzle” – Space Charge Signin MCZ Si irradiated by 24 GeVprotons??
E. Verbitskaya et al., 9 RD50 Workshop, CERN, Geneva, Oct 16-18, 2006
19
Simulation of DP E(x) profile with a consideration of carrier trapping to midgap energy levels:
E(x) and Neff(x) vs. V
Parameters:
introduction rate of generation centers mj
introduction rate of midgap deep levels, DA and DD concentration ratio k = NDA/NDD
bias voltage V temperature T detector thickness d initial resistivity (shallow donor concentration No)
midgap DLs: DD: Ev + 0.48 eV simulation is based on
DA: Ec – 0.52 eV Shockley-Read-Hall statistics
E. Verbitskaya et al., 9 RD50 Workshop, CERN, Geneva, Oct 16-18, 2006
20
Simulation: Evolution of Double Peak E(x) at various NDA/NDD
Fn = 51014 cm-2
V: 100-1000 VNo = 11012 cm-3
d = 300 m, RT
0.0E+00
1.0E+04
2.0E+04
3.0E+04
4.0E+04
5.0E+04
6.0E+04
7.0E+04
0 0.005 0.01 0.015 0.02 0.025 0.03x (cm)
E(x
) (V
/cm
)
100 V
200 V
300 V
400 V
500 V
600 V
800 V
1000 V
k = 1.2
0.0E+00
1.0E+04
2.0E+04
3.0E+04
4.0E+04
5.0E+04
6.0E+04
7.0E+04
0 0.005 0.01 0.015 0.02 0.025 0.03x (cm)
E (
V/c
m)
100 V
200 V
300 V
400 V
500 V
600 V
800 V
1000 V
k = 1
0.0E+00
1.0E+04
2.0E+04
3.0E+04
4.0E+04
5.0E+04
6.0E+04
7.0E+04
0 0.005 0.01 0.015 0.02 0.025 0.03x (cm)
E (
V/c
m)
100 V
200 V
300 V
400 V
500 V
600 V
800 V
1000 V
k = 0.8
E. Verbitskaya et al., 9 RD50 Workshop, CERN, Geneva, Oct 16-18, 2006
21
E(x) and Neff vs. VFn = 51014 cm-2
0.0E+00
1.0E+04
2.0E+04
3.0E+04
4.0E+04
5.0E+04
6.0E+04
7.0E+04
0 0.005 0.01 0.015 0.02 0.025 0.03x (cm)
E (
V/c
m)
100 V
200 V
300 V
400 V
500 V
600 V
800 V
1000 V
k = 1
-1.5E+13
-1E+13
-5E+12
0
5E+12
0 0.005 0.01 0.015 0.02 0.025 0.03
x (cm)
Ne
ff (
cm
-3)
200 V
300 V
400 V
500 V
600 V
800 V
1000 V
k = 1RT
Neff is vastly non-uniform and E is non-linear even at maximal V of 1000 V
E. Verbitskaya et al., 9 RD50 Workshop, CERN, Geneva, Oct 16-18, 2006
22
Evolution of Double Peak E(x) vs. NDA/NDD
Fn = 51014 cm-2
MCZ Si No = 3.51012 cm-3 d = 300 mm, RT
0.0E+00
1.0E+04
2.0E+04
3.0E+04
4.0E+04
5.0E+04
6.0E+04
7.0E+04
8.0E+04
0 0.005 0.01 0.015 0.02 0.025 0.03x (cm)
E (
V/c
m)
100 V
200 V
300 V
400 V
500 V
600 V
800 V
1000 V
k = 1.5
E at p+ contact changes insignificantly: correlates to neutron irradiation
0.0E+00
1.0E+04
2.0E+04
3.0E+04
4.0E+04
5.0E+04
6.0E+04
7.0E+04
0 0.005 0.01 0.015 0.02 0.025 0.03x (cm)
E (
V/c
m)
100 V
200 V
300 V
400 V
500 V
600 V
700 V
800 V
k = 0.5
Major junction at p+ side:correlates to proton irradiation
E. Verbitskaya et al., 9 RD50 Workshop, CERN, Geneva, Oct 16-18, 2006
23
Experimental results: current response fit and E(x) reconstruction in MCZ Si detectors
Goal:
simulation/fit of detector DP pulse response,
reconstruction of electric field profile from current pulse shape,
considering detector structure with three regions: W1, Wb and W2
E. Verbitskaya et al., 9 RD50 Workshop, CERN, Geneva, Oct 16-18, 2006
24
E(x) reconstruction and adjustment to midgap level modelNeutrons, Fn = 51014 cm-2, MCZ Si
0
20
40
60
0 5 10 15 20time (ns)
Cu
rren
t (u
A)
experiment
fit
V = 285 V
Parameters derived by adjustment:
mj = 0.7 cm-1
DD Ev + 0.48 eV 5·1014 cm-3
DA Ec - 0.52 eV 6.75·1014 cm-3
k = 1.350.0E+00
5.0E+03
1.0E+04
1.5E+04
2.0E+04
2.5E+04
3.0E+04
3.5E+04
0 0.005 0.01 0.015 0.02 0.025 0.03x (cm)
E (
V/c
m)
E(x) reconstructionadjustment
285 V
E(x) reconstruction
0.0E+00
1.0E+04
2.0E+04
3.0E+04
4.0E+04
5.0E+04
0 0.005 0.01 0.015 0.02 0.025 0.03x (cm)
E (
V/c
m)
236 V
285 V
334 V
PTI-CZ-d11
At high Fn and V negative SCR extends inside detector bulk
E. Verbitskaya et al., 9 RD50 Workshop, CERN, Geneva, Oct 16-18, 2006
25
Reconstruction of E(x) from DP response:influence of processing
p+ n+
E1
Eb
E2
W1 Wb W2
Electric field gradient dE/dx and Neff in the region adjacent to p+ contact are differentand sensitive to detector processing
HIP-CZ-66 PTI-CZ-C11
tau_e (ns) 4 5Neff1 (c m-3) 1.41E+11 1.09E+12Neff2 (c m-3) 9.46E+12 9.51E+12E_b (V/ c m) 500 1500
Fn = 51014 cm-2 p+
E. Verbitskaya et al., 9 RD50 Workshop, CERN, Geneva, Oct 16-18, 2006
26
Reconstruction of E(x) from DP response:Protons, Fp = 11015 cm-2, MCZ Si + annealing
PTI-CZ-e4, Fp = 1e15 cm-2
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
4.5E+04
0 0.005 0.01 0.015 0.02 0.025 0.03x (cm)
E (
V/c
m)
before anneal
35 min
715 min
1075 min
300 V
Annealing of DP response
0
0.2
0.4
0.6
0.8
1
1.2
0 5 10 15 20 25 30time (ns)
cu
rre
nt n
orm
aliz
ed
0
1: 10
2: 35
3: 85
4: 175
5: 355
6: 715
7: 1075
t_ann (min):
PTI_cz_e4Fp = 1e15 cm-2V = 300 V
-5.0E-05
0.0E+00
5.0E-05
1.0E-04
1.5E-04
2.0E-04
2.5E-04
3.0E-04
0 5 10 15 20
time (ns)
curr
ent
(A)
Series1
Series2
Series3
Series4
Series5
Series6
Series7
Series8
Series9
Series10
Series11
Series12
Series13
Series14
Series15
Series16
Series17
Series18
Series19
Proton, 1e15 cm-2Pti_cz_e4
p+ sidebefore anneal
PTI-CZ-e4, Fp = 1e15 cm-2
0.0E+00
5.0E+03
1.0E+04
1.5E+04
2.0E+04
2.5E+04
3.0E+04
0 0.005 0.01 0.015 0.02 0.025 0.03x (cm)
E (
V/c
m)
200 V
360 V
200 V
360 V
annealing
E. Verbitskaya et al., 9 RD50 Workshop, CERN, Geneva, Oct 16-18, 2006
27
E(x) reconstruction and adjustment to midgap level model Fp = 51014 cm-2, MCZ Si, PTI-CZ-e4
PTI-CZ-e4, Fp = 1e15 cm-2
0.0E+00
5.0E+03
1.0E+04
1.5E+04
2.0E+04
2.5E+04
3.0E+04
0 0.005 0.01 0.015 0.02 0.025 0.03x (cm)
E (
V/c
m)
reconstruction
adjustment
360 V
mj = 0.7 cm-1 – like for neutrons
DD Ev + 0.48 eV 6.6·1014 cm-3
DA Ec - 0.52 eV 3·1014 cm-3
k = 0.45
Parameters derived by adjustment:
k(n)/k(p) 3
correlates to (n)/(p) 4
E. Verbitskaya et al., 9 RD50 Workshop, CERN, Geneva, Oct 16-18, 2006
28
-2.0E-05
0.0E+00
2.0E-05
4.0E-05
6.0E-05
8.0E-05
1.0E-04
0 5 10 15 20 25 30
time (ns)
cu
rre
nt
(A)
43V
88V
135V
205V
275V
298V
321V
367V
404V
440V
Fp = 1e15 cm-2Pti_CZ_e4Annealing 1075 minLaser to p+ side
Protons, Fp = 11015 cm-2, MCZ Si, annealing
• In MCZ Si detectors irradiated by 24 GeV protons electric field extends over entire detector thickness. The major junction is at the p+ contact and SCR is charged positively.• Under annealing E(x) profile becomes more symmetric with increasing V.
PTI-CZ-e4, Fp = 1e15 cm-2, t_ann = 1075 min
0.0E+00
1.0E+04
2.0E+04
3.0E+04
4.0E+04
5.0E+04
0 0.005 0.01 0.015 0.02 0.025 0.03x (cm)
E (
V/c
m)
300 V
400 V
E. Verbitskaya et al., 9 RD50 Workshop, CERN, Geneva, Oct 16-18, 2006
29
Conclusions
Approach of E(x) distribution with a consideration of electric field in the base region allows E(x) reconstruction in detectors irradiated by high F irrespective to the irradiation type.
In heavily irradiated detectors electric field distribution is vastly non-uniform and shows double peak shape with positively and negatively charged regions. Full depletion implies that electric field extends over entire detector bulk and carrier collection is drift process.
Different balance of DDs and DAs induced by neutrons and protons results in the essential difference of E(x) profile, pulse shape and collected charge at the same bias voltage.
In neutron irradiated MCZ Si detectors E at the major junction (n+ side)
decreases with voltage that is favorable for detector operation.
In MCZ Si detectors irradiated by 24 GeV protons the major space charge region is adjacent to the p+ contact and has a positive space charge.
E. Verbitskaya et al., 9 RD50 Workshop, CERN, Geneva, Oct 16-18, 2006
30
Acknowledgements
This work was supported in part by:
• RD50 collaboration,• INTAS-CERN project # 03-52-5744,• RFBR project SS # 00-15-96750
Thank you for your attention!
E. Verbitskaya et al., 9 RD50 Workshop, CERN, Geneva, Oct 16-18, 2006