The measurement of the SiPM photon detection efficiency at...

Fermi National Accelerator Laboratory, October 2006

The measurement of the SiPM photon detection efficiency at ITC-irst

Nicoleta Dinu

INFN – Trento, Italy

Nicoleta Dinu 2Fermi National Accelerator Laboratory, October 2006

• Photon Detection Efficiency (PDE) of the SiPM

• Experimental methods used for the PDE measurement

• PDE of the first SiPM prototypes developed at ITC-irst

• Summary and outlook

Outline


Photon detection efficiency of the SiPM

geomtriggeringSiPM PQE εη ××=

1. QE – the quantum efficiency• probability that a photon generate an e/h pair in the active region of the device (e.g. n+/p

junction of a pixel) - wavelength dependent

a) transmission efficiency through ARC b) internal quantum efficiency(ARC = stack of dielectric layers with appropriate thickness and refraction index)

sourcelightbyemitedphotonsofnrrecordedpulsesoutputofnr

. .

=ηTraditional PDE:

PDE of the SiPM:

p+

πpn+

Anti-ReflectiveCoating (ARC)

SiPM pixel

p+

πpn+

ARC

SiPM pixel


Total area includes dead regions given by:• quenching resistors• trenches• metal layers

Active area: • ∼ 15- 30% of total area

depending of the layout design

(design not in scale)

-VbiasBack contactp+ silicon wafer

Front contact

ppnn++ppππ nn++

Active area

Trenches with Al

Rquenching

hhνν

Photon detection efficiency of the SiPM (cont)2. Ptriggering – the triggering probability (Pt = Pe + Ph - Pe*Ph)

• probability that a carrier (e or h) traversing the high field region triggers an avalanche• Pe & Ph are linked to the impact ionization rates of the electrons and holes

• electrons have higher ionization rates than holes• both electrons and holes ionization rates increase with the electric field (e.g. overvoltage)

3. εgeom – the geometrical efficiency (active area / total area)

SiPM


The experimental set-up

Halogen white lamp(OSRAM)

Neutral filters(filter transmittance 10%)

Monocromator(Jobin Yvon HR250)

Photodiode (UDT 221)

SiPM + preamplifier

Optometer

Stage with 3D micrometric movement (50µm precision)


The methods for the PDE measurement

surfaceSiPMtheonphotonsincident

SiPM thebyrecordedphotonsSiPM N

N

=η

surface SiPMthe onphotonsincidentN

reference calibrated detector(photodiode)

hcλΦN mmW

mmsphinc⋅= )

2/(2//. .

SiPMthecorded by photons reN

DC methodqG

IIN

SiPM

darklight

mms phrec ⋅−

=2//..

Pulses counting method

counts/s) (dark - counts/s) (lightNmms phrec

2//..=

1

2

(for low optical power densities)


1.E+05

1.E+06

1.E+07

1.E+08

1.E+09

1.E+10

1.E+11

1.E+12

300 350 400 450 500 550 600 650 700 750

wavelength (nm)

Nr.

of in

cide

nt p

hoto

ns/ s

/ mm

^2

Set-up calibration

1.E+05

1.E+06

1.E+07

1.E+08

1.E+09

1.E+10

1.E+11

1.E+12

300 350 400 450 500 550 600 650 700 750

wavelength (nm)

Nr.

of in

cide

nt p

hoto

ns/ s

/ mm

^2

0 filter1st filter2nd filter3rd filter1+2 filters calculated1+2+3 filters calculated1+2 filters measured

hcλΦN mmW

mmsphinc⋅= )/(

2

2//. .

)/(

)(

)()/(

2

2 1WA

A

mmmmW

phot

phot

phot RI

A⋅=Φ

no filters

1 filter2 filters3 filters

Photodiode sensibility:• ~ 4 x 107 photons/s/mm2

Calibration method:• light beam without any filter• each filter separately• each filter factor is calculated at all

wavelengths• if 2 or 3 filters are inserted

simultaneously, the optical power density is calculated based on each filter factor determined previously


1.5V overvoltage: y = 0.0652x + 8772.82.0V overvoltage: y = 0.0844x + 168112.5V overvoltage: y = 0.1109x + 106523.0V overvoltage: y = 0.1261x + 179103.5V overvoltage: y = 0.1461x + 244344.0V overvoltage: y = 0.1674x + 30282

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.0E+08

1.E+05 1.E+06 1.E+07 1.E+08 1.E+09

incident photons /s/mm^2

reco

rded

pho

tons

/s/m

m^2

2.0V overvoltage: y = 0.0824x + 5054.32.5V overvoltage: y = 0.1004x + 6517.63.0V overvoltage: y = 0.1222x + 4809.33.5V overvoltage: y = 0.1424x + 103324.0V overvoltage: y = 0.1618x + 11199

1.E+04

1.E+05

1.E+06

1.E+07

1.E+08

1.E+05 1.E+06 1.E+07 1.E+08 1.E+09

incident photons /s/mm^2

reco

rded

pho

tons

/s/m

m^2

PDE @ 550nm – DC & pulses counting methods (1) DC method

device with εgeom ~ 22%


Pulses counting method

qGII

NSiPM

darklightmms phrec ⋅

−=2//..

counts/s) (dark - counts/s) (lightNmms phrec

2//..=


PDE @ 550nm – DC & pulses counting methods (2)

Very good agreement in between the DC and counting pulses methodsPDE increases linearly with the overvoltage at least up to 5V overvoltage

0

5

10

15

20

25

0 1 2 3 4 5

Overvoltage (V)

PDE

@ 5

50nm

(%)

Pulses counting methodDC methodLinear (Pulses counting method)Linear (DC method)


0

2

4

6

8

10

12

14

16

18

300 400 500 600 700 800 900

wavelength (nm)

PDE

%

1.5V overvoltage2.0V overvoltage2.5V overvoltage3.0V overvoltage3.5V overvoltage

0

2

4

6

8

10

12

14

16

18

300 400 500 600 700 800 900

wavelengths (nm)

PDE

%

1.5V overvoltage2.0V overvoltage2.5V overvoltage3.0V overvoltage3.5V overvoltage4.0V overvoltage

Photon detection efficiency – DC method device with εgeom ~ 16%


Maximum PDE in the range 500 ÷ 600 nm

• ~ 16% @ 4V overvoltage for a SiPM of εgeom ~ 22%

For low λ• the PDE is reduced by the Ptriggering

(only holes trigger the avalanche)For high λ

• the PDE is reduced by the QE(QE was optimized for low λ)


Quantum efficiency

30

40

50

60

70

80

90

100

110

300 400 500 600 700 800 900

wavelengths (nm)

QE

%

0V-1V-2V-3V-4V-5V

diode with A = 1mm2

30

40

50

60

70

80

90

100

110

300 400 500 600 700 800 900

wavelengths (nm)

QE

%

0V-1V-2V-3V-4V -5V

diode with A = 0.5625mm2

Diode:• Test structure with the same (n+/p

junction + ARC) as each SiPM pixel• Works as a photodiode at low

reversed bias (0V, 1V or 2V)• Allows the measurement of the QE

(transmission through ARC & internal quantum efficiency)

The impact ionization effect already visible at 3-4V

QE > 95% in the blue region(optimized for λ~ 420nm)


1.5V overvoltage2.0V overvoltage2.5V overvoltage3.0V overvoltage3.5V overvoltage

0

10

20

30

40

50

60

70

80

90

100

300 400 500 600 700 800

wavelengths (nm)

Trig

gerin

g pr

obab

ility

%

0102030405060708090

100

300 400 500 600 700 800

wavelengths (nm)

Trig

gerin

g pr

obab

ility

%

1.5V overvoltage2.0V overvoltage2.5V overvoltage3.0V overvoltage3.5V overvoltage4.0V overvoltage

Triggering probability


device with εgeom ~ 16% Calculated from:

geomtriggeringSiPM PQE εη ××=

Only holes trigger the avalanche

Both holes and electrons trigger the avalanche

Only electrons trigger the avalanche


Light absorption

13

14

15

16

17

18

19

20

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2depth (um)

Dop

ing

conc

.

0E+00

1E+05

2E+05

3E+05

4E+05

5E+05

6E+05

7E+05

E fie

ld (V

/cm

)

DopingField

pn+

h e

At low wavelengths only the holes cross the high field region & trigger the avalanche⇒ triggering probability @ low λ (e.g. 385, 390, 395nm) = hole triggering probability

At high wavelengths only the electrons cross the high field region & trigger the avalanche⇒ triggering probability @ high λ (e.g. 700nm) = electron triggering probability

Simulated doping profile and electric field of the SiPMAttenuation of the light intensity in silicon (Beer-Lambert law)


0.00

0.20

0.40

0.60

0.80

1.00

1.20

0 1 2 3 4 5

Overvoltage (V)

trigg

erin

g pr

obab

ility

hole probability (390nm)hole probability (395nm)electron probability (730nm)Lineare (hole probability (390nm))Lineare (hole probability (395nm))Lineare (electron probability (730nm))

Electron & hole triggering probability

Pholes

Pelectrons

Pe & Ph increase linearly with the overvoltage up to 4VThe slight difference of 0V point could arises from the unavoidable statistical variation of the Vbreakdownacross the structure

Ref. data: W. Oldham & all,• “Triggering phenomena in avalanche

diodes”, IEEE Trans. on Electron Devices Vol. ED-19, No.9, Sept. 1972


Photon detection efficiency of the SiPM devices developed at ITC-irst

Two experimental methods:• DC & pulses counting• very good agreement in between the two methods (λ=550nm)

Photon detection efficiency:• Depends of three factors:

• geometrical efficiency: ~15-30% (e.g. function of the layout design)• quantum efficiency: > 95% in the blue region (optimized for 420nm)• triggering probability: Pe > Ph

• Maximum in the range 500-600 nm :• ~ 16% @ 4V overvoltage for a device of εgeom= 22%• for low λ it is reduced by the Ptriggering (only holes trigger the avalanche)• for high λ it is reduced by the QE (optimized for blue region)

• Increases linearly with the overvoltage (at least up to 4V overvoltage)

Summary

The measurement of the SiPM photon detection efficiency at...

Documents

Transcript of The measurement of the SiPM photon detection efficiency at...