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The new generation of SPAD
Single Photon Avalanche Diodes arrays
Salvatore Tudisco
I Workshop on Photon Detection - Perugia 2007
The collaboration started in the
2004 to realise single device and
first array prototypes
- The Silicon Photomultiplier
- Arrays for imaging
Microelectronics
SPAD
High Boron (P+) concentration
reduce the Breakdown voltage
p-n junction reversely biased above the
breakdown voltage
N-
CMOS planar technology
cathode
P+
1 m SiO2
Si <100>
Buried junctions p--p+ -n- :
P+ sinkers: reduce the contact
resistance of the anode and provide a
low resistance path to the avalanche
current
N- gettering region: impurities
reduction
• P- high Breakdown voltage to prevent peripheral effects
• P+ to reduce the series resistance substrate insulation integration of many elements
E. Sciacca et al., IEEE Trans. on el. dev. 50 (2003) 4
E. Sciacca et al., IEEE Photonics Tech. Lett. 18 (2006) 15
Many elements integration
simple quenching strategy
Psasive Quenching
100 k
50
SPAD Signal
Rise time: 500 ps
Fall time: 30 ns
Recovery time: 1,5 s
(increase with RL)
Important for the applications (SiPM)
SPAD PERPORMANCES
Photodetection Efficiency
Dark Counting Rate
Timing
Afterpulsing
Photodetection Efficiency
E.V. 10%
E. Sciacca et al., IEEE Trans. on el. dev. 50 (2003) 4
M. Belluso et al. Mem. SAIT Suppl. 9 (2006) 430
SPAD PERPORMANCES
Photodetection Efficiency
Dark Counting Rate
Timing
Afterpulsing
d=20 m
SPAD
cooler
counter
S. Privitera et al. submited to NIMA
Single photon regime
SPAD PERPORMANCES
400
Photodetection Efficiency
Dark Counting Rate
Timing
Afterpulsing
350
Counts
300
Many photons regime
9000
250
200
TRIGGER
60 ps
TDC
100
7000
50
6000
0
laser pulse
408 nm
60 ps FWHM
5000
4000
Laser
150
8000
Counts
120 ps
10
CH #
SPAD1
CH #
SPAD2
10,5
11
11,5
12
Time [ns]
3000
Diffusion tail carrier diffusion in neutral
layer delay to avalanche trigger
2000
1000
0
10,5
11
Time [ns]
11,5
S. Tudisco et al. Nuclear Physics B – proc. supl. 150(2006)317
Finocchiaro et al. IEEE Trans. on Nucl. Scie. 52(2005)3040
SPAD PERPORMANCES
Photodetection Efficiency
Dark Counting Rate
Timing
Afterpulsing
Single photon regime
laser pulse
337 nm
resolution 2 ns
+ dye for wave
length-shift
Many photons regime
SPAD PERPORMANCES
Photodetection Efficiency
Dark Counting Rate
Timing
Afterpulsing
TRIGGER
Dark event
Multi Hits
TDC
CH #
After-Pulses
Distribution of successive
events to a primary
avalanche
uncorrelated dark counts
S. Privitera et al. Submit. To NIMA
SPAD PERPORMANCES
Photodetection Efficiency
Dark Counting Rate
Timing
Afterpulsing
Power law ?
the two contributions in 10 s
After the subtraction of the
uncorrelated dark background
S. Privitera et al. submit. to NIMA
SPAD ARRAY:
1st prototype 5x5
20 m diameter, 160 m pitch
Anodes
Dark count rate distribution over 750
pixels (30 arrays)
E. Sciacca IEEE Photonics Technology Letters
18 (13-16) (2006) 1633
SPAD ARRAY
Optical Cross-Talk
the avalanche multiplication process
produce photons
Isolation trench
- 80 m attenuation length
- 10-5 photons per carrier crossing the junction
2mV/div
Electrical Cross-Talk
A1
A5
100 mV/div
1st observation
Induction; field fluctuations Common Substrate
S. Privitera et al. submit. to NIMA
SPAD ARRAY
Time and Spatial correlations
TRIGGER
Pixel 5-1
Multi Hits
TDC
CH #
Piexls 4-1, 4-2, 4-3, 3-1, 1-1
Two contributions:
Prompt < 2 ns Delayed 2 ns 3 s
START
Probability:
Prompt 10-5
Delayed 10-3
SPAD ARRAY
Cross-Talk STOP
Time and Spatial
correlations
Afterpulses 5-1
-Cross-talk and Afterpulsing similar trend,
different slop
- No correlation with distances
S. Privitera et al. Submit. to NIMA
SiPM Configuration
Laser Pulse
= 408 nm
FWHM = 50 ps
VA
RL
SPAD
IOUT
QDC channels
Oscilloscopio
QDC
ADC
QDC or ADC channels
S. Privitera et al. submit. to NIMA
A.Campisi et al. NIM A 571 (1-2) (2007)350
Laser Pulse
= 408 nm
FWHM = 50 ps
Event generator
n° fired pixels
parm. intensity
Pixel ON
Montecarlo
Simulations
Cross-talk generator
parm. Probability
Cross-talk generator
parm. dispersion
Increasing
the probability
Fill the spectrum
Decreasing
the dispersion
Conclusion
Single device performances (20m)
• PDE: ~ 45% @ 550 nm
• Dark counting rate: ~ 400 cps @ 25 °C, ~ 100 cps @ 15°C 20
• Timing: ~ 160 ps many-photons regime, ~ 300 ps single photon regime
• Afterpulsing: ~ 10-3 pulses for primary avalanche
Limitations:
• full recovery ~ 1,5 s
5X5 Array performances (20m)
• Dark Counts uniformity: ~ 10%
• Cross-Talk: prompt ~ 10-5 pulses for trigger
delayed ~ 10-3 pulses for trigger
No distance dependence
• SiPM configuration: poor resolution
peak sensing (ADC) better then charge sensing (QDC)
2007 - 1st SiPM prototype (~ 5000 pixels), 1st array for imaging