uv sensitive very high pde sipms with very low x-talk razmik mirzoyan 1, pavel buzhan 2, boris...

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

3

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.



4

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



5

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 %



6

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.



7

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



8

Entire light emission spectrum of SiPM

Mirzoyan, et al., NIM A 610, 2009



9

(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



10

P. Buzhan, B. Dolgoshein, et al., NIM A 610, 2009



11

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



12

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



13

Over-voltage, V

X-talk for 1mmx1mm SiPM



14



15

• 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



16

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



17

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

uv sensitive very high pde sipms with very low x-talk razmik mirzoyan 1, pavel buzhan 2, boris...

Documents