Characterisation of radiation-damaged SiPMs · C-V measurements and $% &,’(,$(- Upper limit $(< 5...
Transcript of Characterisation of radiation-damaged SiPMs · C-V measurements and $% &,’(,$(- Upper limit $(< 5...
Characterisation of radiation -damaged SiPMs
1. Aims2. SiPMs + measurements3. Results
3.1 C-V: Electrical parameters and doping profile3.2 Idark : Vbd, DCR 3.3 PHdark : DCR3.4 PHlight : photo-detection
4. Conclusions + next steps
ICASP - Schwetzingen --- Robert Klanner --- 11-15.6.2018 1
S. Cerioli, E. Garutti, R. Klanner, D. Lomidze, S. Martens, J. Schwandt, M. Zvolsky
Hamburg University
Aims + SiPMs investigated
Aim: Develop and test methods to characterise hadron-damaged SiPMs Demonstrate them on a specific SiPM which is the best method? Which parameters change with fluence? physics of damage Improvements? Quantify optimal operating conditions + pulse shapi ng for a given task
SiPM: KETEK MP15 *) with 4384 pixels 15x15 µm 2
n-irradiated at JSI (reactor) to 10 9, 1011, 5⋅1011, 1012, 5⋅1012, 1013, 5⋅1013, 5⋅1014 cm -2
ICASP - Schwetzingen --- Robert Klanner --- 11-15.6.2018 2
e h MP15
- Depth ampli-region ~ 1µm- Vbd 27.5 V at 20°C- Voff Vbd – 850 mV
- Rq poly-Si
*) SiPM well studied @ UHH (RK. et al., NIM-A 854 (2016) 70)
Measurements
ICASP - Schwetzingen --- Robert Klanner --- 11-15.6.2018 3
C/G-V: V = 0…26.5V, = 100 Hz…2 MHz T = -30°C and +20 °C
Cse
rial[F
]R
seria
l[Ω
]
Idark : V = -2…+35 (40) V, T = -30°C and +20 °C
°C
12 mA current limit →
used in analysis
Measurements
ICASP - Schwetzingen --- Robert Klanner --- 11-15.6.2018 4
Current transients: V = 27.7…30.5V, T = -30°C PHdark and PH light -spectra for 15 … 75 ns
PHdark PHlight
lightdark
Φ=1012cm -2
lightdark
Φ=0 Φ=5⋅1013cm -2npe = 1 npe ≈ 100
gate:gate:
used in analysis + used in analysis
Parameters and formulae for analysis
ICASP - Schwetzingen --- Robert Klanner --- 11-15.6.2018 5
EQF and ENF determined from high statistics Φ=0 data at +20°C for mostcases a small correction
find: EQF ≈ ENF
0 1 2 3 4 5 6 7 81
1.05
1.1
1.15
1.2
1.25
1.3
V - Vbd [V]
EN
F
+20°C
Cpix … pixel capacitanceRq… quenching resistanceCq … quenching capacitance
Vbd … breakdown voltageVoff … Geiger turnoff voltage
DCR … dark count rate
EQF … excess charge factor
ENF … excess noise factor /!
/!
PDE … photon detection efficiencyµ … no. photons initiating Geiger discharge
μ
pulse shape (slow comp.): # $%&⋅'(
) ($%& + $()⋅( )⋅
( … fraction of signal in gate)
-$'⋅⋅)( .)
μ⋅)⋅
μ⋅)!⋅!⋅
3 ways to obtain µ +
)
∙∙0
N.B: valid if no saturation effects !
1 23mV from high statistics Φ=0 dataat +20°C assume 1
does not depend on Φ, T
Vbd versus V off
From PH-fits: )() find )() d)/d⋅( ) with d)/d=const
straight line describes )() from extrapolation to ) .( .)
for 43ns (compatible results for other values ):
5)/d 9.75⋅104 V-1 (compare to: $%&/( 17.8 fF/1.6⋅10-19C = 11.1⋅104 V-1 ≈ ok)
1 850 mV
ICASP - Schwetzingen --- Robert Klanner --- 11-15.6.2018 6
V [V]
Idar
k[A
] Gain
24 25 26 27 28 29 30 31 32 331 10 14−
×
1 10 13−×
1 10 12−×
1 10 11−×
1 10 10−×
1 10 9−×
1 10 8−×
1 10 7−×
1 10 6−×
1 10 5−×
0
2 105×
4 105×
6 105×
8 105×
Idark-E0Idark-E9Idark-E11Gain-E0Fit
Vbd
Voff
Difference: 1 850 mV to be taken into account for analysis
for further analysis assume no dependence of 1 on 6
d)/d ≈ compatible with $%&/(
C-V measurements and $%&, '(, $(
- Upper limit $(< 5 fF (~1 fF-pulse shape)- Significant differences for SiPM samples
ICASP - Schwetzingen --- Robert Klanner --- 11-15.6.2018 7
Cpi
x[fF
]R
q[k
Ω]
Dependence of $%& and '( on and 6 (neutron fluence):
$%& not influenced by and 6
'( increases with decreasing (poly-Si)'( appears to increase for 6 8 .. cm -2
Cq
Cpix
Rpar C/V
Rq
x Npix
SiPM model
C-V measurements: Doping and E -field
Doping profile (&)and E-field (&)assuming 1-D abrupt p +n-junction:
ICASP - Schwetzingen --- Robert Klanner --- 11-15.6.2018 8
[k
V/c
m]
Minor decrease of for 6 = 5⋅1014 cm -2
(expected from radiation-induced donor removal)
°C, & !9V
[c
m-3
]
°C, & !9V
5⋅1014Φ=0
Breakdown voltage V bd
ICASP - Schwetzingen --- Robert Klanner --- 11-15.6.2018 9
1 using max( :-) with
Only at +20 °C measured for all SiPMs for 6 variations observed
difference 1(6) 1(6 )significant only at 5 ⋅1014 cm -2
1 ≈ const. up to ≈5⋅1013 cm -2
Increase by ≈ 300 mV at 5 ⋅1014 cm -2
Fluence [cm -2]
1 108× 1 109
× 1 1010× 1 1011
× 1 1012× 1 1013
× 1 1014× 1 1015
×
26.3
26.4
26.5
26.6
26.7
0
≈
Vbd
[V]
°C
Dark current vs. fluence and voltage
Does ( 1) scale with 6? ' (6)/ (...)vs. 1
ICASP - Schwetzingen --- Robert Klanner --- 11-15.6.2018 10
(6)/ (...) increases with 1: higher 6 faster increase
; 1 ' const ; for 8 1increase by factor up to 2 with
Model: -$'⋅($%&⋅( ))⋅ x2 by and gain implausible
assume change due to DCR “trap assisted high-field generation”?
E11
5E14
3− 2− 1− 0 1 2 3 4 5 6 7 8 90.9
1.1
1.3
1.5
1.7
1.9
2.15E11/E115E12/E11E13/E115E13/E115E14/E11
V - Vbd [V] C
urre
nt r
atio
norm. to 1
5E11
5E14
E13
5E115E13
currentlimit
-$' vs. fluence and voltageModel: -$'⋅($%&⋅( ))⋅ assume $%& .2 fF(1 23 mV and 0from 6 data)
ICASP - Schwetzingen --- Robert Klanner --- 11-15.6.2018 11
(6, <) allows estimation of -$'(6,<)
-dependence of -$' very different after irradiation! Exponential increase for 1 8 !V + saturation at high 6
Comment: Estimate fraction of busy pixels (occupancy) (-$'⋅#)/%& 0.5 for -$' 1011 s-1, # 20 ns, %& 4384
PHdark – irradiated SiPM () vs. Φ at -30°C:
ICASP - Schwetzingen --- Robert Klanner --- 11-15.6.2018 12
1 pulse (=/#)/# per sec in random gate :
>. – #(. =/#) Solid curves, which describe data ( # 20 ns)
) 1 no CN (corr. noise) : >.⋅-$'
) @1 no CN: )!⋅>.⋅-$'
+ CN: Var ⋅!⋅)!⋅>.⋅ABC
(N.B. only valid in absence of saturation)
dependence of described by model for 10 11; 6 ;5⋅1012 cm -2
allows to estimate # and DCR (if no strong saturation effects )
Φ=5E14
Φ=0
Φ=E9
…poor
fits
PHdark – irradiated SiPM – -$'
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-$'-results agree within ≈ 30 % with results from
-method more complicated and range of validity limitedDifferences may help to better understand rad.damage effec ts on SiPMs ???
Var ⋅!⋅)!⋅>.⋅ABC → -$'
∙!∙)!∙(
–#(.=D/#))
Comparison of and method
Comparison:
ICASP - Schwetzingen --- Robert Klanner --- 11-15.6.2018 14
Typical agreement E(30%), however also larger differences
Detailed comparison + understanding of differences still to be done
PHlight : ) determinationCan we determine ) ?
)
∙
.
∙
ICASP - Schwetzingen --- Robert Klanner --- 11-15.6.2018 15
Yes, up to ~10 12 cm -2; No for higher fluences – saturation!
27 27.5 28 28.5 29 29.5 30 30.5 31 31.5 320
0.1
0.2
0.3
0.4
var/(mean x ENF x ESF)Cpix x (V-Voff)
V [V]
Gai
n[1
06 ]
Φ=060 ns gate
/
27 27.5 28 28.5 29 29.5 30 30.5 31 31.5 320
0.1
0.2
0.3
0.4
var/(mean x ENF x ESF)Cpix x (V-Voff)
V [V]
Gai
n [1
06 ]
Φ=5⋅1011cm -2
60 ns gate/
27 27.5 28 28.5 29 29.5 30 30.5 31 31.5 320
0.1
0.2
0.3
var/(mean x ENF x ESF)Cpix x (V-Voff)
V [V]
Gai
n[1
06 ]
Φ=5⋅1012cm -2
60 ns gate
/
27 27.5 28 28.5 29 29.5 30 30.5 31 31.5 320
0.2
0.4
var/(mean x ENF x ESF)Cpix x (V-Voff)
V [V]G
ain
[10
6 ]
Φ=1013cm -2
60 ns gate
/
PHlight: µ-determination
Can we determine F ? (µ = no. of photons initiating a Geiger discharge)
ICASP - Schwetzingen --- Robert Klanner --- 11-15.6.2018 16
0 3 gate 60 10 14 10
27 27.5 28 28.5 29 29.5 30 30.5 31 31.5 320
100
200
mean/(G x ESF)var/(G^2 x ENF x ESF^2)mean^2 x ENF/var
V [V]
mu
3 gate 60 10 14 10
27 27.5 28 28.5 29 29.5 30 30.5 31 31.5 320
100
200
mean/(G x ESF)var/(G^2 x ENF x ESF^2)mean^2 x ENF/var
V [V]
mu
5 gate 60 10 14 10
27 27.5 28 28.5 29 29.5 30 30.5 31 31.5 320
100
200
mean/(G x ESF)var/(G^2 x ENF x ESF^2)mean^2 x ENF/var
V [V]m
u
Φ=060 ns gate
Φ=5⋅1011cm -2
60 ns gate
Φ=5⋅1012cm -2
60 ns gate
27 27.5 28 28.5 29 29.5 30 30.5 31 31.5 320
200
400
600mean/(G x ESF)var/(G^2 x ENF x ESF^2)mean^2 x ENF/var
V [V]
mu
Φ=1013cm -2
60 ns gate
Yes, ; !G. 3 V + up to ~10 12 cm -2; No for higher fluences – saturation!
Most reliable:
)∙
3 ways to determine µ
μ
) ∙
μ
)! ∙ ∙ !
μ ! ∙
with )
$%&⋅( )⋅
PHlight : µ (∝ PDE) photo -detection
ICASP - Schwetzingen --- Robert Klanner --- 11-15.6.2018 17
1 108× 1 109
× 1 1010× 1 1011
× 1 1012× 1 1013
× 1 1014× 1 1015
×
0
100
200
300V - Vbd = 1VV - Vbd = 2VV - Vbd = 3VV - Vbd = 3.5V
Fluence [cm^-2]
mu
0
6 ; ..: PDE essentially unaffected by irradiation6 .. 3⋅..: irradiation affects PDE (low 1 still ok)
6 3⋅..J
: SiPM not a useful photo-detector „ all pixels occupied “
( „ “ optimisation under way)
T = -30°C60 ns gateμ
) ∙
μ
)! ∙ ∙ !
μ ! ∙
Conclusions + next steps1. C-V, Idark , PHdark , PHlight measured at -30 °C for Φ = 0 … 5⋅1014 n/cm 2
2. Formulae presented, which relate SiPM parameters to me asured quantities
3. Cpix and Rq little affected by Φ
4. Idark DCR increase with V and Φ high DC pixel occupancy for Φ > 1013
expect a significant PDE reduction
5. PHdark DCR from variance ~consistent with DCR from I dark
6. PHlight different methods indicate Gain not affected by Φ
7. PHlight approximate V- and Φ-dependence of „relative“ PDE (µ)
for Φ=5⋅1014 cm -2 and –30°C SiPM investigated not a useful photo-detector
Next steps:1. DCR-“PDE“ as a function of ( 6,, ) + noise vs. threshold as function of ( 6,, )
2. Optimisation of pulse-shaping how much can one gain?
3. Include fast component from $( in analysis
4. Implement saturation effects due to dark counts + photo ns
5. Implement what we learn in Schwetzingen
ICASP - Schwetzingen --- Robert Klanner --- 11-15.6.2018 18
Most methods of SiPM characterisation fail after high Φ irradiation??? Can we find + agree on the most suitable methods ???