APD photodetectors in the Geiger photon counter mode

Modelisation of Geiger mode avalanche
photodiodes for photon counting. counting
Presented by D. PELLION
Collaboration : in CESR : R. BAZER-BACHI
V. BORREL
C. MAGENC
J.L COURECH
in LAAS : D. ESTEVE
F. THEREZ
F. BONY
1 2005

2
Summary
• Introduction
Light detection, state of art
Objective of this work
• Avalanche photodiodes in Geiger mode (Geiger ( Geiger-APD APD)
Principle
• Modelization
physical Modelization
electrical Modelization
• The reading and control circuit
• Experimental visualization
test bench
samples of oscillograms
• Conclusion
Utilization of these results to define the technology of a Geiger APD

3
Introduction
• Photomultipliers (PMT),
• Avalanche Photodiodes (APD).
• Objective of this work
– Avalanche Photodiodes in Geiger mode (Geiger ( Geiger-APD APD). ).
Multiplication
Estimated Performances
PM APD Geiger-APD
10 6 to 10 9 50 to 100 10 3 to 10 9
Photon counting Yes No Yes
Quantum efficiency 20% 80% 80%
T=20°C
λ= optimal

4
Avalanche photodiodes in Geiger
mode (Geiger-APD)
• Geiger Polarization
I
Principle of the Geiger mode
Performances
Problems, Problems,
Limitations
Zone A Zone B
Vrepos Vav VG Figure 3 : static behaviaur of a p-n jonction
Now: dead time is 1ns to 10ns
V
Zone A Zone B
V G
V av
V
V repos
I
Event
dead time
Figure 1 : Voltage across the photodiode
Figure 2 : Current across the photodiode
t
t

Modelization
• Physique Modelization
di ( t )
dt
M ( t )
V
( t )
=
=
=
v
M ( t ) ⋅ ⋅ i(
t )
w
fct ( V ( t ), t )
1 t
V G − ∫ i ( t ). dt
C i
0
i(t) increasing or decreasing exponential
i
V
VG VAV V static
M(t) Experimental
10
V(t) charge of the capacitor from Vrepos to VG
discharge of a capacitor from VG to Vav
5
104 VG to Vav 103 10 5
10 4
10 3
Gain in Geiger mode
1
2 3
Dark counts
5 6
2 3
1
Gain in Geiger mode
G = Cpix.(Vbias – Vbreak)/e
6
t
t
V G -V AV
V G -V AV

6
Modelization
• Electrical Modelization (VHDL-AMS)
(VHDL AMS)
Vdiode = V G
Cd
Rd
I
V av
Cd : represents the capacitance of the
photodiode : 1pF
Rd : to model the decrease of the
polarization of the photodiode during the
avalanche : 100 Ohms
I : the closing of I induces a voltage
drop from V G to V AV

V 20
V 140
The reading and control circuit
Rch
A
R 4
T4
APD
(Cd, Rd)
R 3
C
T3
Avalanche active quenching electronics.
R 2
T2
T1
B
R 1

8
Experimental Visualisation
• mesuring circuit
circuit to visualize the avalanche
• Results
VG Vav V repos
1,3µs
V 1 = 25V V repos = 140V
R1 = 1k
V R1
G
S
D
V DS
V D1
R2 = 50
V R2
1 mA
0 V
1,3µs
Terminal Voltage of the photodiode Current across the photodiode

I(mA)
5 mA
0 mA
Estimation of the amplification :
Gain in Geiger mode
0,1 ns
t(s)
(19 mA * 100 ps) / 2 = 9,5*10-13 coul.
8*10-14 coul. / 1,6 *10-19 coul. = 6 000 000 electron.
Or G = Cpix.(Vbias – Vbreak)/e
= 1pF * 1V /q
= 6 000 000 electron

10
Conclusion
• Fabrication of Geiger diodes
Low voltage
Small capacitance
Very small noise current (thermal)
• Fabrication of an array of Geiger diodes
Next results to be presented
metal
L eff
P +
P +
N ++
P -