APD MPR July 24th 2002 D. Renker PSI 1

Avalanche Photo-Diodes (APDs)

K.Deiters, Q.Ingram, D.Renker, T.SakhelashviliPaul Scherrer Institute, Villigen, Switzerland

J.Grahl, I.Kronqvist, R.Rusack, A.Singovski, P.VikasUniversity of Minnesota, Minneapolis, USA

I.Britvitch, A.Kuznetsov, Y.Musienko, S.Reucroft, J.SwainNortheastern University, Boston, USA

Z.Antunovic, N.Godinovic, I.SoricUniversity of Split, Croatia

Honorary assistent: J-L.Faure

2D. Renker PSIAPD MPR July 24th 2002

APD History

Late 1992: 1st Hamamatsu prototype

Early 90th Push for a homogeneous calorimeter

1995: Test of an APD on a PbWO4 crystal in H4

1996-97: APDs chosen for ECAL

A comparison of the response to 80 GeV electrons of a lead tungstate crystal with a PIN diode (top) and an APD (bottom) read-out. The tail to the right of the peak in the PIN diode spectrum is due to particles leaking out of the back of the 18 cm long crystal and passing through the diode

APD MPR July 24th 2002 D. Renker PSI 3

APD propertiesAPD properties

0

10

20

30

40

50

60

70

80

90

100

300 400 500 600 700 800 900 1000

Wavelength [nm]

Quantum Efficiency [%]

0.1

1

10

100

1000

10000

0 50 100 150 200 250 300 350 400 450

Voltage [V]

Gain

0

10

20

30

40

50

60

0 500 1000 1500 2000

Gain

1/M*dM/dV [%]

-30

-25

-20

-15

-10

-5

0

0 500 1000 1500 2000

Gain

1/M*dM/dT [%]

APD MPR July 24th 2002 D. Renker PSI 4

APD properties cont. (1)APD properties cont. (1)

1

3

5

7

9

11

13

15

0 500 1000 1500 2000

Gain

Excess Noise Factor

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

0 500 1000 1500 2000 2500

Gain

Dark Current/Gain [nA]

10

100

1000

10000

0 100 200 300 400

Voltage [V]

Capacitance [pF]

APDs are insensitive to magnetic fields, are compact, cheap and have a small nuclear counter effect. They are potentially radiation hard.

But: they have a small area (5x5 mm2) and they were a widely unknown device

APD MPR July 24th 2002 D. Renker PSI 5

0

10

20

30

40

50

Mar-99 Jul-99 Oct-99 Jan-00 May-00 Aug-00 Nov-00 Feb-01 Jun-01

date of delivery

VB - V

R

[V]

ProductionPrototypes

Error bar shows range within delivery

0

100

200

300

400

500

600

30 35 40 45 50

VB - VR

Frequency

Stable since 2000

Distance of operating to breakdown voltageDistance of operating to breakdown voltage

.

Side remark: Thousands of APDs have been tested and sometimes “accidents” happened. APDs were biased with the wrong polarity for a long period or the bias voltage was far too high (3000 V instead of 300 V). No APD ever died due to such an event.

APD MPR July 24th 2002 D. Renker PSI 6

Reliability testsReliability tests

Weak or bad APDs are identified by a number of tests after the 60Co irradiation:

is there a change of the breakdown voltage (dVb)? is the dark current at gain 50 within the limits (Id)? Is the dark current divided by the gain falling continuously (Id/M vs M)? Is there an abnormal high noise? Is the APD coming from a “bad position” on the wafer (mask problem)? Is the APD coming from a “bad wafer” (problem in the neutron irradiation)?

The same tests are performed after the annealing with the exception of the noise. The noise is later on measured in Lyon when the APDs have been mounted on the capsule.

How do we measure these parameters? Yuri

How efficient is the screening? Quentin

What are the rejection criteria? Sasha

APD MPR July 24th 2002 D. Renker PSI 7

PROVISIONAL FINAL TECHNICAL SPECIFICATIONPROVISIONAL FINAL TECHNICAL SPECIFICATION

General conditions: VR (operating voltage for gain M = 50) and VB (breakdown voltage, at which the dark current exceeds 100 A), asall other values measured at T = 25 C. For radiation hardness: neutron (1 MeV) fluence 2x1013 n/cm2

Sensitive area 5x5 mm2

Survival rate after irradiation * 99.9 0.1 %Survival rate after 2 months at 90º C @ M=50 * 99.9 0.1 %

Survival rate after 1 day at 20 A (V = VB + 20V) (1) * 99.9 0.1 %

Passivation layer Si3N4

Charge collection within 20 ns (2) 99 1 %

Capacity at VR (mean value) 65 – 85 pF

Spread of capacity at VR 5 pF

Capacity at VR – Capacity at VB 3 pF

DM/dV·1/M (gain sensitivity to voltage) at VR 3.5 %/VQuantum efficiency (mean value) (3) 75 5 % @ 430 nmSpread of measured quantum efficiency (3) 7 %

Operating voltage VR 340 – 440 V

Difference VB - VR ** 37 V

Nuclear counter effect leff (4) < 7 m

Excess noise factor at VR 2 0.3 @ 430 nm

Dark current Id at VR 50 nASerial resistance (mean value) < 5 Spread of serial resistance 1 DM/dT·1/M (gain sensitivity to temperature) at VR 2 0.5 %/deg CelsiusRatio of Noise (M=300)/Noise (M=50) (5) 12Variation of Id/gain for 50 < M < 400 (6) < 10% rise Change of QE after irradiation 2 %Change of gain after irradiation (7) 3 % Dark current (bulk) after irradiation (7) 5 A

Spread of Id (total) at VR after irradiation (7) 0.5 A

Difference VB-VR after irradiation (7) > 30 V