J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004. CERN RD39 Collaboration: Cryogenic...
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Transcript of J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004. CERN RD39 Collaboration: Cryogenic...
J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.
CERN RD39 Collaboration: Cryogenic Tracking Detectors
RD39 Status Report 2004
Jaakko Härkönen Helsinki Institute of Physics, Finland
Zheng Li Brookhaven National Laboratory, USA
J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.
CERN RD39 Collaboration: Cryogenic Tracking Detectors
OUTLINE
•Trapping: A limiting factor for detector operation •RD39 Strategy for radiation hardness up to 1016
neq/cm2
•Charge Injected Detector CID•Experimental results•Cryogenic detector module activities•Summary•Workplan for 2005
J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.
CERN RD39 Collaboration: Cryogenic Tracking DetectorsTrapping: A limiting factor for detector
operation
tthNvt
1 The trapping time-constant
is not dependent on T
The thermal velocity vth saturates at 20 kV/cm E-field to 107cm/s1016 neq/cm2 irradiation produces NT3-5*1015 cm-3 with 10-
15cm2 Particle generated charge carrier drifts 20-30m before it gets trapped regardless whether the detector is fully depleted or not ! 1016 neq/cm2 radiation load: 80-90% of the volume of d=300m detector is dead space !
J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.
CERN RD39 Collaboration: Cryogenic Tracking Detectors
HOW A TRAP CAN BE NEUTRALIZED ?
By filling them with current/charge or light injection.
0
2
4
6
8
10
12
14
16
18
100 150 200 250 300
T(K)
Q (
arb
. un
its)
Qcol
Qpol
•p+np+ symmetric structure irradiated to 3.75·1015 cm–2
•Bias potential 300 V (Qcol) or 0 V (Qpol ; the electric field is induced by the polarization of the detector)
•The p+np+ detector with this fluence can be operated already at 100 V bias
•Standard p+nn+ detector would deplete fully only above 1 kV bias at this fluence
CID (Charge Injected Detector) irradiated with 3,8*1015 n/cm2
J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.
CERN RD39 Collaboration: Cryogenic Tracking Detectors
DETRAPPING
The detrapping time-constant depends exponentially on T
kTECth
td eNv /
1
If a trap is filled (electrically non-active) the detrapping time-constant is crucial
For A-center (O-V at Ec-0.18 eV with 10-15 cm2 )
T(K) 300 150 100 77 60 55 50 45 40
d 10ps
10ns
10s
6ms
12.3s
5min
3,6 h
15 days
13 years
J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.
CERN RD39 Collaboration: Cryogenic Tracking Detectors
RD39 Strategy for radiation hardness up to 1016 neq/cm2
The detector CCE can be considered to be a product of two factors:
tdrttGF ed
wCCECCECCE /
,
Depletion term
Trapping term
o Electric field manipulation to increase depletion depth w (original Lazarus effect) CCEGF ~ 1
o Freeze out trapping effect at T lower than LHe T CCEt ~ 1
J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.
P+ P+
Jp
Jp = epμE
divJ=0
divE=ptr
E(x=0) = 0 (SCLC mode)
E(x) ~ V √ X
J(V) = V2
E(x)
The key advantage: The shape of E(x) is not affected by Nmgl, and stable at any fluence
Current injected detector (principle of operation)
xd
+
J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.
E(x) E(x)E(x)E(x)
x x x x
Ohmic mode
p>>ptr
E(x) = V/d J ~ V
“Diode” mode
p>ptr
E(x) ~ E(0) + ax
DL saturation p >> ptr E(x) = ax
SCLC mode
Ndl>ptr
E(x) ~ SQR(x) J ~ V2
Evolution of E(x) in CID with the injected current
J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.
log J
log V
Ohmic, J ~ V
SCLC, J ~ V2
DL saturation
“Diode”
I-V characteristic of CID
Proof of CID concept: – observation of SCLC and DL saturation behavior
Problem: - optimal range of V for CID operation
J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.
CID I-V simulation
Sample parameters Physical constants Calculated valuesd [cm] 0.035 eps0[F/m] 8.85E-14 mu [cm2/V*s]
Uc[V] 0 eps 11.7 VsN0[cm-3] 0.00E+00 q[C] 1.60E-19 Vth*Nc 4.13E+26Operation parameters k[J/K] 1.38E-23 Vth*Nv 1.25E+26
Ub [V] 30 oe [cm 2̂/Vs] 2.08E+03 Nc[cm-3] 2.1741E+19Temperature 250 vse [cm/s] 1.12E+07 Nv[cm-3] 8.6963E+18
dX [cm] 1.00E-04 be[T] 7.82E-01 ni[T],cm-3 7.23E+07
injected current oh [cm 2̂/Vs] 8.17E+02
Egen, eV 0 vsh [cm/s] 8.14E+06 IntN(d) 0.00E+00
Sig(e), cm2 0.00E+00 bh[T] 9.87E-01 Vth(e),cm/s 1.90E+07
Sig(h), cm2 0.00E+00 Eg (eV0 1.12 Vth(h),cm/s 1.44E+07
M, cm-3 0.00E+00 Parameter Ef, eV 0.56Jn [A/cm2] 0.00E+00 Calculated Ef, eV 0.01 DL #
Jp [A/cm2] 1.00E+00 D/A, 0/1 0 1 0 1electrons holes electrons holes electrons holes electrons holes
Et=Edl-Ev 1.117 0.6 0.48 0.64 0.55 0.57
E(x) calculation sig/e[cm2] 1.00E-15 1.00E-17 1.00E-15 5.00E-15
Iterations 2 Imin, A/cm2 1.00E-12 sig/h[cm2] 1.00E-15 1.00E-15 1.00E-15 5.00E-15
Kdesipaiton 0.8 points 50 Ndl[cm-3] 0.00E+00 0.00E+00 2.80E+12 0.00E+00
Imax, A/cm2 1.00E+00 Sig*Vth 1.90E-08 1.44E-08 1.90E-10 1.44E-08 1.90E-08 1.44E-08 9.49E-08 7.19E-08
detrap.prob. 3.59E+11 3.97E-12 1.39E-01 1.03E-01 5.31E-02 2.69E+01 6.82E+00 5.23E+00
Row X E0(x) E1(x) n(x) p(x) Ff(x) Neff(x) Ff(x) Neff(x) Ff(x) Neff(x) Ff(x) Neff(x)
# cm V/cm v/cm cm-3 cm-3
I-V calculationMACRO
shallow donors deep acceptor deepdonor shallow acceptors
0.0E+0
5.0E+3
1.0E+4
1.5E+4
2.0E+4
2.5E+4
3.0E+4
0 0.01 0.02 0.03 0.04 0.05
E(x)
0.0E+005.0E+121.0E+131.5E+132.0E+132.5E+133.0E+13
0.00 0.02 0.04 0.06
Neff
1.E+001.E+021.E+041.E+061.E+081.E+101.E+121.E+14
0.00 0.02 0.04 0.06
n(x)p(x)
start
CID I-V simulation software
J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.
A12, Cz(PTI), P+- N - N+, Fn=1015cm-2
1.E-10
1.E-09
1.E-08
1.E-07
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
1 10 100 1000
Bias, V
Cu
rren
t, A
/cm
2
180k
200k
220k
250k
Fit 180K
Fit 200K
Fit 220K
Fit 250K
CID I-V characteristics
J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.
CID I-V characteristics
1,E-10
1,E-09
1,E-08
1,E-07
1,E-06
1,E-05
1,E-04
1,E-03
1,E-02
1 10 100 1000 10000
Voltage (V)
Cu
rre
nt d
en
city
(A
/cm
2)
5e14 cm-2
1e15 cm-2
3e15 cm-2
Fit
Fit
Fit
Fit, 1e16 cm-2
Experimental and simulated IV’s of CIDs @ 220K
Decreasing I with fluence !!
J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.
Fn=1015cm -2, T=220K
1.E-03
1.E-02
1.E-01
1.E+00
1.E+01
1.E+02
1.E+03
1 10 100 1000
Bias, V
Cu
rre
nt,
μA
/cm
2
Wacker FZ, BNL
Wacker FZ, HIP
Cz HIP
Wacker FZ, PTI
Cz, PTI
Reproducibility of CID technology(detector dark current)
J=V2/d3
J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.
0
100
200
300
400
500
600
700
800
900
1000
0.0E+00 5.0E+14 1.0E+15 1.5E+15 2.0E+15 2.5E+15 3.0E+15 3.5E+15
Fluence, n/cm2
Th
res
ho
ld v
olt
ag
e,
V
FZ, Wacker, BNL
FZ, Wacker, HIP
ZC, HIP
FZ, Wacker, PTI
CZ, PTI
Reproducibility of CID technology(threshold voltage)
Vthr= Ntr·d2
Vthr~ Φ·d2
J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.
CCE measurements
Injection mode
Standard mode
J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.
• Silicon P+ - n – N+ and P+ - n – P+ structures heavily irradiated by neutrons operate in SCLC mode with hole injection
• The I-V threshold voltage and the dark current are in the range of hundreds volts, which fits to the detector application requirements
• CID I-Vs are stable under irradiation
• Technology of CIDs is developed with pre-irradiation by neutrons
• No effect for the detector performance by:– type of Si – technology
• The developed software for CIDs engineering allows proper simulation of I-Vs with two key physical parameters:
– Deep trap activation energy of 0.48eV from the valence band– Deep trap concentration proportional to fluence
Conclusions
J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.
CERN RD39 Collaboration: Cryogenic Tracking Detectors
CHARGE INJECTION SUMMARY
If a trap level is filled (say, by current or charge injection) and then frozen (very long detrapping time) at cryogenic temperatures, this trap level will no longer be able to trap free carriers again, and it becomes electrically inactive.
In this case, the CCE can be improved as well to a value close to 1
CCE can be increased close to 1 by manipulating the electric field in the detector via current and/or charge injection at temperatures from 130 K to 150 K.
Feasible solution for very high luminosity colliders ?
J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.
CERN RD39 Collaboration: Cryogenic Tracking Detectors
LOW TEMPERATURE SUMMARY
Readout electronics becomes faster and has lower noise
No leakage current >> low electrical power from HV supply
Low depletion voltage (original Lazarus effect)
CCE increase without reduction of detector thickness (increase of charge collection depth)
J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.
CERN RD39 Collaboration: Cryogenic Tracking Detectors
RD39 RESOURCES
*Device processing: Brookhaven National Laboratory BNL (USA), Ioffe PTI
(Russia), Helsinki Institute of Physics HIP (Finland).
*Irradiations: protons (Accelerator Laboratory,Univ. of Jyvaskyla,Univ. of
Karlsruhe) neutron (Jozef Stefan Institute JSI, Ljubljana) 60Co (Brookhaven National Laboratory)
*Characterizations:CCE JSI, FCT Algarve University, Faro, Portugal DLTS Univ. of Florence, PTI TCT BNL, PTI
CV/IV Practically all member institutes
J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.
CERN RD39 Collaboration: Cryogenic Tracking Detectors
RD39 WORKPLAN FOR 2005
Device Physics and Basic Research • Optimization of Deep Level (DL) spectra by CID pre-irradiation and intentional contamination. • CCE measurements on CID pre-irradiated by protons and neutrons• Strip detectors based on CID approach (strips). •Completetion of LH TCT setup construction at CERN cryolab.
1. Testing of new etching techniques of edgeless detectors. 2. Improving the cryomodule operation below 200K3. Module construction of CID strip detectors.
Cryomodules