Charge Collection in Single-Column 3D Detectors
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Transcript of Charge Collection in Single-Column 3D Detectors
Charge Collection in Single-Column 3D Detectors
Carlo Tosi, Mara Bruzzi
INFN and University of Florence
Monica Scaringella, Hartmut F.-W. Sadrozinski, Alek Polyakov
SCIPP, UC Santa Cruz
M. Boscardin, C. Piemonte, A. Pozza, S. Ronchin and N. Zorzi
ITC-irst
G.-F. Dalla Betta
DIT, Università di Trento
Analysis of CCE - V on 3D sensors
SensorsP-type strip-like Sensors ~500m thick, ~150 m single columns (n+/p)
Depletion Pattern on 3D:C-V and Cint-VConsequences for CCE
2 CCE systems: Beta source 90Sr with scintillator trigger Analog DAQ (Firenze)
2 sec shaping time, pad sensor Binary DAQ (Santa Cruz)
100 ns shaping time: strip sensor
Cint-V 1MHz
5
6
7
8
9
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0 20 40 60 80 100 120 140 160 180Bias [V]
Cin
t [p
F]
Depletion Pattern on 3D SSD: C-V and Cint-V
1/C2 (10 kHz)
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
0 20 40 60 80 100 120 140 160 180
Bias [V]
1/C
2 [1
/pF2 ]
Voltage Range 2:region between col.is fully depleted depletion proceedsonly towards the back(almost like a planar diode)
full depletion ~200Vdepletion width of ~150+350m
Voltage Range 1:region between col.is not fully depleted large capacitance
full dep. between columns~ 7V
Depletion Pattern CCE PatternMean collected charge & Inefficiency
Voltage Range 2 (bias > ~7 V):region between columns is fully depletedDepletion depth = tw
-> Charge collected = 4fC*(tw/300m)-> No Inefficiency
tc
tw
a b
Voltage Range 1 (bias < ~7V): there are lateral depleted regions near each column which are tc in depth. Charges generated by traces like b are not collected.-> Charge collected = 4fC*(tc/300m) ~ 2fC-> Inefficiency = fraction of un-depleted area
between columns
Analog DAQ (Firenze) : Pad Sensor
Inefficiency(ideally, not measured here!)
Most probable Charge
Inefficiency = fraction of undepleted areaMean charge ~ depleted thickness
Pad Sensor Analysis Analog DAQ (Firenze) with deconvolution software
(NIKHEF)
150V
Discrepancy between pulse height and simulated Landau is observed at high voltage. Most probable value of pulse height is determined by Landau deconvolution only in the range 0-60V. At 70-150V the most probable value taken is max of pulse height spectrum.
Applied Voltage = 5V
Pulse Height Max
mp from Landau deconv
0 50 100 15020
40
60
80
100
120
max
pul
se h
eigh
t [a.
u.]
Voltage [V]
Fz Si, W = 525m
Sc-3D D4 diode configuration
Efficiency vs. Threshold
0
0.2
0.4
0.6
0.8
1
0.5 1 1.5 2 2.5 3 3.5 4 4.5Charge (fC)
Eff
icie
ncy
6 V
0 V
30 V
Binary DAQ (Santa Cruz) Strip Sensor
(We define the median as the collected charge)
At 6V:Collected charge = 1.7 fCAs expected from 140 m Inefficiency = 0i.e. un-depleted area = 0
At 0V:Collected charge ~ 1fCInefficiency > 80%?
At 30V:Collected charge = 3.0 fCAs expected from 280 m Inefficiency = 0i.e. un-depleted area = 0
?
Median charge
Most likely charge
Reconstruction of Pulse Height Spectrum
Mean Charge and Inefficiency
Efficiency vs. Bias Voltage
0
0.2
0.4
0.6
0.8
1
0 5 10 15 20 25 30
Bias Voltage (V)
Eff
icie
nc
y
Collected charge:Increases with bias voltage(Square root behavior beyond ~7V?Not yet saturated at 150 V)
Efficiency varies only below ~ 7V,~ 100 % beyond.
CCE in p-type 3D SSD
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1
2
3
4
5
6
0 50 100 150 200
Bias Voltage [V]
Co
llec
ted
Ch
arg
e [
fC]
Median
Most Likely
Binary DAQ (Santa Cruz)
Collected charge: compares well with Ansatz Q = 1fC + const/C
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0 20 40 60 80 100 120 140 160
Voltage (V)
Ch
arg
e (
fC)
Median Charge (fC)
Expedted Q from 1/C
Charge Collection Comparison: Pads vs. SSD, 100 ns vs. 2.4 s
All data normalized at 150 V bias.
Good agreementbetween UCSC (100ns) and FI (2.4s).
Higher active thickness than from C-V i.e. d ~ 1/C (diffusion?)
0
100
200
300
400
500
600
0 50 100 150 200Voltage [V]
Act
ive
Th
ickn
ess
[um
]
Florence
C-V
UCSC
ConclusioConclusionsns
Charge Collection vs. voltage confirms simple picture of depletion in single-column 3D sensors:
• Rapid depletion between columns (< 10 V)• Slow, planar-diode like depletion beyond that• Voltage dependence of charge collection about same for SSD (100 ns) and pads (2.4 s)• Collected charge larger than predicted from 1/C at lower voltages
Ackgnowledgments::
ITC-irst team for production of 3D detectorsClaudio Piemonte for the very nice graphics of depletion process