uv sensitive very high pde sipms with very low x-talk razmik mirzoyan 1, pavel buzhan 2, boris...
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UV Sensitive very high PDE SiPMs with very low X-talk
Razmik Mirzoyan1, Pavel Buzhan2, Boris Dolgoshein2, Elena
Popova2, Masahiro Teshima1
1- Max-Planck-Institute for Physics, Munich, Germany2- National Research Nuclear University MEPhI, Moscow, Russia
MEPhI - MPI for Physics R&D collaboration and cooperation with PerkinElmer Industries (now EXCELITAS)
Developing UV sensitive SiPMs with extremely high PDE,
Extremely low crosstalk and low dark rate
SiPM Sizes 1x1 and 3x3 mm²
µ-cell pitch 50 and 100 µm
Geom. Eff. 40-80%
Pioneer and great Leader: Prof., member of Russian Academy of Sciences Boris Dolgoshein
1930-2010B. Dolgoshein, R. Mirzoyan, E. Popova, P. Buzhan, PEI, et al.,
16-17 February 2011
Saturday 11 June 2011, TIPP-2011, Chicago
R. Mirzoyan: UV sensitive high PDE, low X-talk SiPM
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Current status of SiPM• Currently there is a lot of enthusiasm about the new devices
but the deep understanding is not simple, it comes only slowly
• One of the main problems of SiPMs is its low PDE, that is not easy to measure. It shall be disentangled from the cross-talk and after-pulsing.
• The after-pulsing in PMTs is a ~1% effect on single ph.e. level, while for example, for currently existing MPPC’s from Hamamatsu it is a 20-30 % (depending on type and the applied over-voltage) effect.
• Often the real value of PDE is significantly lower than the claimed (advertised) one. The reasons are a) the low applied overvoltage, b) neglecting of the cross-talk (X-talk) and c) of the after-pulsing.
Saturday 11 June 2011, TIPP-2011, Chicago
R. Mirzoyan: UV sensitive high PDE, low X-talk SiPM
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Still trying to understandThe PDE of a SiPM can be presented as
PDE(PDE() = Geiger-eff. x Geometry-eff. x Internal-QE ) = Geiger-eff. x Geometry-eff. x Internal-QE x Transmission(x Transmission())
Geiger-eff. = Function (applied-over-voltage);
when Geiger-eff. saturates, one can obtain stable operation, also in the
sense of temperature
Saturday 11 June 2011, TIPP-2011, Chicago
R. Mirzoyan: UV sensitive high PDE, low X-talk SiPM
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0,0 2,5 5,0 7,5 10,00
25
50
75
SiPM 1x1 mm2. T = +20 0C.
(Ubreakdown
= 31,46)
P
ixel
gai
n k pi
xel ,
105
Overvoltage U, V
0,0 2,5 5,0 7,5 10,00
10
20
30
40
50
PD
Effi
cien
cy ,
%
Overvoltage U, V
= 310 nm
Overvoltage +15 %
Overvoltage +20 %
Overvoltage = operational voltage – breakdown voltage (~31.5V)
A PDE and gain of a 1x1 mm² SiPM test-sample produced by MEPhI-MPI cooperation;
@+20°C• As one can see on the right top the PDE of SiPM saturates at an over-voltage V/V ~15 %• For higher applied V/V the gain (and the noise) will still increase but there will be no further increase of PDE• Hamamatsu MPPCs operate at maximum V/V < 3 %
Overvoltage +10 %
Overvoltage + 5 %
Saturday 11 June 2011, TIPP-2011, Chicago
R. Mirzoyan: UV sensitive high PDE, low X-talk SiPM
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Optical X-talk and afterpulsing and PDE• We need to learn how todisentangle the X-talk and the after-pulsing fromthe genuine PDE.
• One can see on the rightthat depending on the PDE measuring method, the X-talk and afterpulsingcontributions together could be as big as the PDE by itself.
Saturday 11 June 2011, TIPP-2011, Chicago
R. Mirzoyan: UV sensitive high PDE, low X-talk SiPM
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Checking the universality of light emission (the culprit for X-talk) from
different SiPM samples• We measured the
absolute light emission of an MPPC of 3mmx3mm size from Hamamatsu and of 3mmx3mm and 1mmx1mm size SiPM test-samples from MEPhI-MPI design
• As one would expect within errors all threesamples emit the same light, the same spectrum
Saturday 11 June 2011, TIPP-2011, Chicago
R. Mirzoyan: UV sensitive high PDE, low X-talk SiPM
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Entire light emission spectrum of SiPM
Mirzoyan, et al., NIM A 610, 2009
Saturday 11 June 2011, TIPP-2011, Chicago
R. Mirzoyan: UV sensitive high PDE, low X-talk SiPM
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(Patent pending)
X-talk suppression is improving the performance
Known ways to suppress X-talk:
a)trenchesb)2nd junctionfor isolating thebulk from the active regionc) new method,shown on right d) special coatings
Saturday 11 June 2011, TIPP-2011, Chicago
R. Mirzoyan: UV sensitive high PDE, low X-talk SiPM
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P. Buzhan, B. Dolgoshein, et al., NIM A 610, 2009
Saturday 11 June 2011, TIPP-2011, Chicago
R. Mirzoyan: UV sensitive high PDE, low X-talk SiPM
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Operating SiPM @ V/V ~ 15 %Gain ≤ few x 106
Peak PDE ~ 60 – 65 % High PDE also in near UV (> 50 %)Timing ≤100 psX-talk ≤ 1-2 %F-factor ≤ 1.02
Ideal SiPM: a good wish or a reality, where are we ?
After-pulsing ≤ 1-2 %Dark rate ≤ 0.5 MHz/mm² (room T°)Size1-10 mm²Low T ° dependence of gain, of PDEScalable matrixesSignal processing on rear side
Saturday 11 June 2011, TIPP-2011, Chicago
R. Mirzoyan: UV sensitive high PDE, low X-talk SiPM
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Improved SiPMs• 18 different variations of SiPM (p over
n) have been produced by MEPhI-MPI cooperation (with the support of PerkinElmer, now Excelitas)
• Many innovative ideas were implemented
Gain linearity
Saturday 11 June 2011, TIPP-2011, Chicago
R. Mirzoyan: UV sensitive high PDE, low X-talk SiPM
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Over-voltage, V
X-talk for 1mmx1mm SiPM
Saturday 11 June 2011, TIPP-2011, Chicago
R. Mirzoyan: UV sensitive high PDE, low X-talk SiPM
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Saturday 11 June 2011, TIPP-2011, Chicago
R. Mirzoyan: UV sensitive high PDE, low X-talk SiPM
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• When V/V is set to~15 %, the Geiger efficiencyis saturated
• As a result dependence on T ° becomes very low,it can be as low as0.5 %/ °C
PDE for 1mmx1mm SiPM
Saturday 11 June 2011, TIPP-2011, Chicago
R. Mirzoyan: UV sensitive high PDE, low X-talk SiPM
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Conclusions• In a time scale of 1-2 years from now one can buy SiPMs
with really outstanding characteristics, probably from several manufacturers.
• Their sizes could span 1-10 mm (in remote future perhaps even larger)
• SiPM cost will be reduced due to the availability of full CMOS designs. Several USD per mm² is not very unrealistic.
• These devices are going to substitute classical PMTs and APD in many (but of course not all) applications, including those in physics instrumentation in, for example, nuclear medicine (time-of-flight PET,…).
• We could demonstrate samples with max. PDE of 50-60 %, X-talk in the range of < 2-5 % and a very high PDE also in the UV when operated at ~15 % over-voltage
Saturday 11 June 2011, TIPP-2011, Chicago
R. Mirzoyan: UV sensitive high PDE, low X-talk SiPM
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Reminder: light absorption in Si
• Absorption of light in Si
• Already from this graph one can get an impressionabout the relevant for theX-talk effect wavelength range
• Absorption length below~370 nm is below 10 nm
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