Transcript HgCdTe avalanche photodiodes development at CEA/Leti-Minatec Johan Rothman CEA: L. Mollard, S. Bisotto Sofradir: X.

2009
2007
HgCdTe avalanche
photodiodes development
at CEA/Leti-Minatec
Johan Rothman
CEA: L. Mollard, S. Bisotto
Sofradir: X. Lefoule, F. Pistone
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Detectors for Astronomy Workshop 2009 - 1
HgCdTe e-APDs at CEA/LETI - Johan Rothman
Outline
HgCdTe e-APD development in France
Why HgCdTe e-APDs?
Performance
 Applications

HgCdTe e-APDs for photon-counting
Focal plane array results
HgCdTe e-APD road map at LETIMinatec and Sofradir
Conclusion/perspectives
2007
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Detectors for Astronomy Workshop 2009 - 2
HgCdTe e-APDs at CEA/LETI - Johan Rothman
HgCdTe e-APD development in France
CEA/LETI
 E-APD technology
and design

Detector lab and fab
Sofradir
 ROIC design
 EO FPA test
 E-APD FPA
industrialisation
Epitaxy, µ-tech.
 E-APD physics and
test
Response time
Multiplication process
(gain, noise)
 Sensitivity limits


2007

 ROIC design
 EO FPA test
System labs
e-APDs
ONERA
 E-APD physics

Multiplication process
(gain, noise)
 EO FPA test
Fab etc..
Astro-physics labs
 LAOG ( Grenoble) and
LAM (Marseille)
Adaptiv optics, fringe
tracking
 Photon-counting imaging

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Detectors for Astronomy Workshop 2009 - 3
HgCdTe e-APDs at CEA/LETI - Johan Rothman
The photodiode: an ideal light detector?
High timing resolution
QE100% i.e. no loss of information
High Sensitivity
Dark currents can be lower than 1 electron/s
 Limited by proximity-electronics (PE) noise
 Can be reduced by amplified photo detection!

2007
M x Photo-current
M
PE noise
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Detectors for Astronomy Workshop 2009 - 4
HgCdTe e-APDs at CEA/LETI - Johan Rothman
APDs Advantages vs. Photo-multipliers or
amplified-CCD
 High Quantum efficiency  100%
 All detection-modes are possible
Photon-counting
Real time measurement of the flux f(t) at high speed
Integration (standard imaging operation) 
 Non-linear geiger mode (avalanche breakdown)



 Small and fast

 t 
  t dt
t int
Compatible with imaging and telecom applications
 …but furious (other than HgCdTe-APDs…)
2007
 Multiplication of both electrons and holes in Si and III-V
material APDs
 Gain is strongly dependent on junction profile High
dispersion (not good for imaging)
 Strong degradation of the SNR: F=SNRSNL/SNRout>2-5 at M>10
 Response time is slowed down at high gain  Limited gainBand-Width product < 340GHz (Intel record, Nature
Photonics, 3, 2008)
 After pulsing probability >0 (photon counting)
 Dead time (photon counting)
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Detectors for Astronomy Workshop 2009 - 5
HgCdTe e-APDs at CEA/LETI - Johan Rothman
Exclusive electron multiplication in HgCdTe
APDs
10000.0
HgCdTe e-APD
lc=5µm, T=80K
Gain M=I/I
CC
Gain
1000.0
100.0
10.0
1.0
-14.0 -13.0 -12.0 -11.0 -10.0
-9.0
-8.0
-7.0
-6.0
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
Bias (V)
Exponential gain without avalanche break down (Beck,DRS, 2001)
2007
 Exclusive




electron multiplication 
Felectric~1-1.2 (DRS, SELEX, LETI, BAE, TELEDYNE)
Response time independent of gain GBW>16THz (LETI)
Low gain dispersion
Noise equivalent input counts Neq_in< 10 000 e/s (LETI, DRS)
Stable up to M>5000 (LETI APD Record, 2006)
PLUS all the standard properties of HgCdTe
High
quantum efficiency (close to 100% internal QE)
Detect wavelengths from visible to IR (with QE~100%)
Low operating temperatures due to small Eg
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Detectors for Astronomy Workshop 2009 - 6
HgCdTe e-APDs at CEA/LETI - Johan Rothman
A new horizon of applications from visible to IR wavelengths with
MCT e-APDs :(M>1000, F~1, Neq_in<10 000 e/s)
 Photon counting
This talk (1)
Quantum optics
 Physics, astronomy, quantum cryptography
 Imaging in Astronomy, biomedical applications, high-energy physics
 Astronomy : higher order correlation functions!

 t 
 Real-time measurements
Telecommunications
Time resolved Raman and Fluorescence spectroscopy, Doppler effect
 Environmental surveillance, element recognition
 Real-time dynamics observations


 Integration (Imaging FPAs)
Active laser assisted imaging
t int
 Long range identification, safe planetary landing (NASA), bio-medical
(fluorescence imaging), observation through semi transparent
surfaces
 Passive amplified imaging
This talk (2)
 Low flux applications ; hyper spectral imaging, wave front detection
for astronomy, high dynamic range

2007
  t dt
 The geiger modes is not (yet) possible due to the absence of
avalanche break-down threshold
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Detectors for Astronomy Workshop 2009 - 7
HgCdTe e-APDs at CEA/LETI - Johan Rothman
Performance optimization of HgCdTe eAPDs?
MW (lc=4.2-5µm) e-APD performances:
M>100,
F=1.2, Ieq_in~10000 e/s, tresp~2 ns, Top<100K
Application
Photon counting
M, F ok
Passive amplified
imaging
M, F, tresp ok
Critical
parameter
1. Reduce tresp :
<100 ps
Reduce Ieq_in :
<1000 e/s
(Operability)
1. Reduce Ieq_in :
< 1000 e/s
2. Increase Top
(Operability)
This talk
E-APD gain (F~1)
for photon
counting
Response time
limits (jitter)
Impact of xCd:
Gain, F, dark
current
(Diodes and FPAs)
2007
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Detectors for Astronomy Workshop 2009 - 8
HgCdTe e-APDs at CEA/LETI - Johan Rothman
Photon counting
Counter : Direct pixel digitalization
Read-out noise supression
 High dynamic range (>16 bit)
 High frame-rate
 Dark-current thresholding

2007
Timer :Estimation of the time of
arrival of the photons
3D imaging
 Quantum optics and imaging
 higher order photon correlation
functions

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Detectors for Astronomy Workshop 2009 - 9
HgCdTe e-APDs at CEA/LETI - Johan Rothman
Exclusive electron multiplication for
Linear mode proportional photon counting
Output count probability distribution for <M>=300 and F=1.04
0.014
probability density
0.012
0.01
1 photon
0.008
2 photons
0.006
0.004
0.002
0
0
2007
100
200
300
400
500
600
700
800
900
Output counts
 Low F Proportional photon counting

Distinguish the number of photons that arrives simultaneously in the
depletion layer (not possible in GM-APDs)
 Reduce after-pulsing effects 0% (GM –APDs ~10%)

High order temporal correlation function A new window for astronomy !
 No quenching  high repetition rates >GHz is possible (GMAPDs ~ 10MHz)
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Detectors for Astronomy Workshop 2009 - 10
HgCdTe e-APDs at CEA/LETI - Johan Rothman
Exclusive electron multiplication for
Linear mode proportional photon counting
Output count probability distribution for <M>=300 and F=1.04
DC generation
0.014
Distributed dark-current
generation
probability density
0.012
p
i
n
0.01
1 photon
0.008
2 photons
0.006
0.004
M
0.002

1  1

ln M diff   M diff
M diff
dark _ cont _ gen
0
0
100
<M>dark
2007
200
300
400
500
600
700
800
900
Output counts
 Low F Proportional photon counting
 Reduce after-pulsing effects (GM –APDs ~10%)
 No quenching  high repition rate >GHz is possible (GM-APDs ~
10MHz)
 Low F  Discrimination of non-amplified dark current Low DCR


Depends on the distribution of the dark current generation
Homogeneous distribution <M>dark=52 for Mdiff=300
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Detectors for Astronomy Workshop 2009 - 11
HgCdTe e-APDs at CEA/LETI - Johan Rothman




Response time optimization in APDs
p
n-
Response time
jitter  limits
the timing
precision
E
Depletion layer =
mutliplication region
n+
 Collection of minority electrons
Collection of
minority electrons
Transit time of e
and h
RC charge
evacuation
2007


Diffusion ~ 1-5 ns1
Drift (xCd gradient)  Vd of e in p type HgCdTe
  50-100 ps jitter3
 Transit time of e and h Vd(E) :

th=10-50ps  GBW limit ~20THz (MW)1,2
 RC charge evacuation ~ 10-50 ps
 Ultimate photon counting timing resolution <100ps!
1.
2.
3.
© CEA 2008. Tous droits réservés.
G. Perrais et al. JEM, 37, 2008
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G. Perrais et al. JEM, 38, 2009
Detectors for Astronomy Workshop 2009 - 12
J. Rothman et al. to be published, JEM, 40 (2010)
HgCdTe e-APDs at CEA/LETI - Johan Rothman
First move towards photon counting (2008):
Active 3D Imaging 4x10 test FPA, 40µm pitch
 CTIA coupled one-shot TOF+R imaging (3D)
Pulse detection in C10 (1)
 Sample time sweep  TOF (2)
 Switch to integrate the total light pulse in C20 (3)

First 3D event driven
(2)pixel
4
Pixel outputs :
TOF noise measured with
a flux of 560/e per pixel, at
M=100 variable delay,
T=80K
Return intensity
Track & Hold
(analog voltage ramp)
Vref
+
N1
OTA
-
Iin
(1)
+
Vth
N2
Lock
T.O.F.
T.O.F. Noise (ns)
Time base
N3
-
C3D
C2D
Vsub<0V
2007
(3)
Precharge
3
2
1
RESET
"Advanced pixel design for infrared 3D LADAR imaging
"
F. Guellec, SPIE DSS, 6940-84
0
0
25 50 75 100 125 150 175 200 225 250 275
laser pulse delay (ns)
 Sequential and spatial DTOF<2ns over 4x10 pixels  range
resolution < 30 cm
 320x256, 30µm pitch array under test today

Objectives: DTOF<2 ns and read noise < 2 e-
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Detectors for Astronomy Workshop 2009 - 13
HgCdTe e-APDs at CEA/LETI - Johan Rothman
Gain performance in e-APDs (xCd)
lc=3.3 µm lc=4.2 µm
MBE
LPE
lc=5.3 µm
LPE
lc=2.9 µm
MBE
lc=2.9 µm
MBE, larger depletion layer
2007
 Exponential gain  exclusive electron multiplication at M>600
for lc=2.9 µm (T=80K)


Hole multiplication is still negliable up to high gains at high xcd
lc=2.9µm is compatible with high operating temperature active laser
imaging (Isat~20pA in VHg doped MCT at T=200K)
 Gain is dependent on junction geometry also at lc=2.9µm
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Detectors for Astronomy Workshop 2009 - 14
HgCdTe e-APDs at CEA/LETI - Johan Rothman
Excess noise factor in lc=2.9µm e-APD (T=80 K)
M=600
M=60
inoise  M 2qI F
M=10
M=1
inoise  2qI
2007
 Noise factor F~1 for lc=2.9 µm MCT e-APD up to
M=600

Noise is √F higher than the shot-noise
 Consistent with a high stability of the exclusive
electron multiplication at high xCd
 Absence of 1/f noise !
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Detectors for Astronomy Workshop 2009 - 15
HgCdTe e-APDs at CEA/LETI - Johan Rothman
e-APD sensitivity :
Equivalent input dark current M=100, T=80K:
I eq _ in
1000
Ieq_in - Icc (fA)
Test array diode
Measurements
without
ROIC
Icc=0, A1, ZF
Icc=0, A2, ZF
Icc, A1, RF
Icc, A2, RF
100
2
iFOV
0

2qM 2 F
10
M=380
1
ROIC needed
0.1
0.01
2007
3.0
3.5
4.0
4.5
5.0
5.5
Cut-off wavelength (µm)
 Ieq_in =200-500 fA at M=100 for lc=5.3 µm
 Strong reduction for shorter lc  Ieq_in~ fA
(10 ke/s)

Needs Low noise ROIC to measure at M<100 or lc<4µm
M<300
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Detectors for Astronomy Workshop 2009 - 16
HgCdTe e-APDs at CEA/LETI - Johan Rothman
320x256 30µm pitch MCT bi-mode e-APD FPA
Success of DEFIR in 2009 (collaboration with Sofradir)
MW e-APD,
lc=5.3µm à 80K
TIA
M
2007
2D identification :
Cactive=30fF (0.3Me, 90 e rms noise)
Passive thermal surveillance
Cpassive=120fF (1.2Me, 150 e rms noise)
Specification
Expected value
Compliance
Max frame rate
450 Hz
(10MHz, 4 outputs)
C
>99.7% from 0% to
90% of ROIC Well-fill
C
100 nsec
C
No parasitic effect
C
7V
C
Linearity
Mini Integration time / gating
Blooming
Max diode reverse bias
3:rd demonstration of large format e-APD FPA for 2D imaging
Selex (2004) , DRS (2006), both with gain operability
99% Workshop 2009 - 17
Detectors of
for Astronomy
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HgCdTe e-APDs at CEA/LETI - Johan Rothman
320x256 30µm pitch MCT bi-mode e-APD FPA
Gain measurements
Test array / FPA gain
f/2, 5V
1000.0
<M>=14.1
s/<M>=7.7%
Op50%=99.84%
Test array gain
FPA average gain
Gain
100.0
10.0
1.0
-9.0
-7.0
-6.0
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
Bias (V)
2007




-8.0
An identical gain is measured in test-arrays and FPAs
Record high 99.8% operability
QE>70%
FPA compatible low gain dispersion (<10%) up to 7V reverse bias

Gain dispersion is dominated by the EPL ripple
 Reduced dispersion by using MBE or reduced ripple EPL
 Excess noise factor Fmax=1.4 (consistent with similar test diodes)
 Excess noise factor operability <F>+/-100%=99.7% up to M=70!
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Detectors for Astronomy Workshop 2009 - 18
HgCdTe e-APDs at CEA/LETI - Johan Rothman
320x256 MW HgCdTe e-APD lc=5.4 µm, T=80 K
(Narrow multiplication layer  tunneling)
4.5V, M=25, C1=120fF, tint=300µs
Ieq_in=70 fA (420 ke/s)
Flux (BB at T=290K)
Zero flux
FOV=0° +
Photon leakage
Ieq_in
3.5V, M=10, C1=120fF, tint=40ms
Ieq_in=10 fA (60 ke/s)
DC generation
2007
M dark 
M
2
diff eq _ in
I
I dark
p
i
Bias
M
Ieq_in (A)
Iobs (A)
<M>dark
<M>cont_gen
2.5
5
5.0E-15
4.0E-14
3.13
2.50
3.5
10
1.0E-14
7.5E-13
1.33
3.90
4.5
25
7.0E-14
7.0E-11
0.63
7.45
n
 <M>dark<< <M>cont_gen. for M>10:

Dark current can be suppressed using photon counting thresholding
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All rights reserved. Any reproduction in whole or in part on any medium or use of the information contained herein is prohibited without the prior written consent of CEA
Detectors for Astronomy Workshop 2009 - 19
HgCdTe e-APDs at CEA/LETI - Johan Rothman
320x256 30µm pitch lc=3.3µm T=80K
Flux (BB at T=290K)
6 V, M=6 (sM/M=2.3%), C1=30fF, tint=2 s
Ieq_in=95 aA (590 e/s)
Zero flux
2007
 Gain ~test array gain
 <Mdark>=2.6 ~ <M>cont_gen=2.7 

continuos GR in the junction at low gain
DC generation
p
i
n
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Detectors for Astronomy Workshop 2009 - 20
HgCdTe e-APDs at CEA/LETI - Johan Rothman
e-APD sensitivity :
Equivalent input dark current M=100, T=80K:
I eq _ in
2
iFOV
0

2qM 2 F
1000
Icc=0, A1, ZF
Icc=0, A2, ZF
Icc, A1, RF
Icc, A2, RF
Ieq_in - Icc (fA)
100
MMW-FPA=10
10
M=380
1
0.1
MSW-FPA=6 (590 e-/s)
0.01
2007
3.0
3.5
4.0
4.5
5.0
5.5
Cut-off wavelength (µm)
Late news data (14/10/2009):
M=24 (12 e-/s) at 10.5V
 Reduction is lower than M=100 trend line
 Evaluation of parameter space is under way

xCd, gain, LPE, MBE hetero-structure APDs
© CEA 2008. Tous droits réservés.
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Detectors for Astronomy Workshop 2009 - 21
HgCdTe e-APDs at CEA/LETI - Johan Rothman
LETI/Sofradir HgCdTe e-APD Road-map
2010
2009
2011
Exclusive electron multiplication HgCdTe APDs
Q2
2D Active/passive FPA
320x256, p30µm
Q3
3D Active FPA
320x256, p30µm
Q4
Real time BW>GHz
Single element
Wavefront/Fringe tracking
320x256, > 1.5kFPS,
noise < 2 e-
Photon counting array
Format to be defined
2007
Q3
2D DTOF imaging
320x256, p30µm
photon counting
Single element
 Optimizing HgCdTe e-APDs

Operability >99.9%, low dark noise (10 e-/s), speed (<100ps)
 Develop dedicated proximity electronics to address a
maximum of applications (RON < 1 e-)
© CEA 2008. Tous droits réservés.
Toute reproduction totale ou partielle sur quelque support que ce soit ou utilisation du contenu de ce document est interdite sans l’autorisation écrite préalable du CEA
All rights reserved. Any reproduction in whole or in part on any medium or use of the information contained herein is prohibited without the prior written consent of CEA
Detectors for Astronomy Workshop 2009 - 22
HgCdTe e-APDs at CEA/LETI - Johan Rothman
Conclusions/Perspectives
 MCT e-APDs

F~1 at M>600 for lc=2.9 µm to 5.4 µm at T=80K
 Linear mode photon counting
Proportional counting (detect 1, 2.. photons)
Discriminate non-amplified dark currents
 Low DCR
 Timing precision  below 100 ps
 No after pulsing is expected


 ROIC (CMOS)-design is the key to harnest the
potential of MCT e-APDs
2007
2D active imaging array
 Neq_in<12 e-/s in lc=2.9 µm array at M=25  enables wave
front sensing
 3D AI array under testing : timing precision~1ns (15cm)

 2010



Low noise-high speed wave front sensor
Neq_in < 1 e-/s at M>10
Single element photon counting
© CEA 2008. Tous droits réservés.
Toute reproduction totale ou partielle sur quelque support que ce soit ou utilisation du contenu de ce document est interdite sans l’autorisation écrite préalable du CEA
All rights reserved. Any reproduction in whole or in part on any medium or use of the information contained herein is prohibited without the prior written consent of CEA
Detectors for Astronomy Workshop 2009 - 23
HgCdTe e-APDs at CEA/LETI - Johan Rothman