9 nov 20111 rad-hard photomultiplier chips™ eric s. harmon, ph.d.brad cox, ph.d. vice president of...
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9 Nov 2011 1
Rad-HardPhotomultiplier Chips™
Eric S. Harmon, Ph.D. Brad Cox, Ph.D.Vice President of Research Professor, Experimental High Energy [email protected]+1 508-809-9052 Chris Neu. Ph.D.
Asst. Prof. , Experimental High Energy PhysicsJim Hyland, Ph.DDavid B. Salzman, Ph.D Bob Hirosky, Ph.D.
Assoc. Prof., Experimental High Energy PhysicsBrian Francis
Mike Arenton, Ph.D. Sasha Ledovskoy, Ph.D.
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Outline
• GaAs Photomultiplier ChipTM
• Radiation damage in semiconductors
– Bulk damage
– Surface damage
– Dark-count rate
• Experimental Setup for GaAs PMC radiation testing
• Next Steps
• Summary
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LightSpin’s GaAs Photomultiplier ChipTM
• Array of single-photon avalanche devices (SPADs):– PMC™ uses GaAs (or GaInP) for direct absorption photonehp– SiPM and MPPCTM use Si for indirect photon+momentumehp
• PMC™ 1 mm 1 mm prototypes in hand• Straightforward scaling
– cm2 active area at high yield– Comparable production cost to SiPM
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Cost?• High Volume silicon CMOS: $700 per 8” wafer = 2.5 ¢/mm2
(http://www.gsaglobal.org/email/2010/general/0222w.htm)
• High Volume GaAs cost: $1,700 per 6” wafer = 10 ¢/mm2
• High Volume silicon = 100s of wafers per week!
• High Volume GaAs = 10s of wafers per week!
• Volume production wins
• Ultimate cost of 1 cm2 detector (in high volume):
– Silicon: $2.5 + packaging + testing
– GaAs: $10 + packaging + testing
• Current costs of SiPMs: $150/cm2 (http://sensl.com/estore/)
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LightSpin Photomultiplier Chip™
• Designed, grew, fabbed, and tested 1 mm2 devices– 400 SPADs per mm2
– Extremely low dark current (10 pA/mm2)
• High fill factor and high detection efficiency:– Single-photon detection efficiency > 20%
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LightSpin Photomultiplier Chip™
• Designed, grew, fabbed, and tested 1 mm2 devices– 400 SPADs per mm2
– Extremely low dark current (10 pA/mm2)
• High fill factor and high detection efficiency:– Single-photon detection efficiency > 20%
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LightSpin GaAs PMC™
• Initial evaluation of radiation hardness mixed:– Devices not designed to be rad hard– Surface vs. bulk radiation damage– Packaging & test issues
• Working on next generation:– 1st generation of Rad Hard GaAs PMC™
• Fab completion due this month– 2nd generation packaging
9 Nov 2011 10
Relative lifetime damageGaAs vs. silicon
• Generation Rate: G = ni V / • Radiation Damage: rad = 1/K• G() ≈ ni V K
variation in neutron damage arises from silicon NIEL curves
9 Nov 2011 11
Relative lifetime damageGaInP vs. silicon
• Generation Rate: G = ni V / • ni(GaInP) ni(GaAs)/1E4
variation in neutron damage arises from silicon NIEL curves
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Radiation Damage Analysis
• For low bias, observe reduction in dark current:
– Radiation induced annealing?
– Similar results reported by Sandia
– Indicative of low “bulk” damage
• For high bias, observe dramatic increase in dark current:
– Surface damage (hopping conduction)
– 1st generation Rad Hard GaAs PMC should not suffer this limitation
9 Nov 2011 1414
LightSpin – UVA collaboration
• Test LightSpin GaAs PMC chips for Radiation Hardness:
– Build new test box for GaAs PMC chips
– Develop printed circuit board to allow testing of multiple devices while under irradiation
– Test multiple devices:
• Individual SPAD elements
• PMC arrays (1.0 mm × 1.0 mm):– Approximately 100, 400, 1600 SPADs/mm2
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Test SetupNew test fixtureunder construction
20 BNCbias cables
DC bias supply(LED driver)
Keithley 7001switch box
Keithley 237SMU
Programmablebias supply
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1st generation PC Board
Front of Board Back of Board
GaAs PMC
SMA
BNC
BiasCopper ground plane
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2nd generation PC BoardDIP Switch –Isolate individualdevices
Optional 50termination
10 LIMO Connectors(100 Gohmsto ground)
Bias connector
Filtered biasto DUT
Die attacharea
RC biasfilter
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Board mounted device Probed mounted device
• Packaging + readout board introduced significant leakage current
DC Current-Voltage non Rad Hard GaAs PMC Characteristics
9 Nov 2011 2020
Next Steps
• 1st generation rad hard GaAs PMC: Nov. 2011
• 2nd generation PCB (improve dark current)
• Improved Test Fixture
• Radiation testing at PS at CERN
– Made contact and discussed irradiations with facility managers.
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Summary• Silicon APDs (including MAPD, SiPM and MPPC) will be unable to withstand the anticipated
high-radiation environment of the endcap electromagnetic detector. Silicon devices also may not be able to be used in portions of the hadronic sections of the endcaps.
• GaAs Photomultiplier Chips™– Predicted to provide more than 100 times more radiation tolerance for neutrons– Predicted to provide 40 – 60 X times more radiation tolerance for protons/electrons
• GaInP Photomultiplier Chips™– Predicted to provide 1E6 times more radiation tolerance for neutrons– Predicted to provide 1E5 times more radiation tolerance for protons/electrons
• LightSpin/UVA collaboration– Completing development of 2nd generation PMC Test Fixture:
• Up to 10 devices can be tested during irradiation• DC and pulsed characterization• Ultra-low leakage design
• 1st generation rad hard GaAs PMC & boards to UVA by end of year• Irradiation regime
– EM– Hadronic– Hadronic + EM– control
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Irradiation materials limitations• Dark count rate & dark current modeled
– Radiation damage factor K
– Thermal generation rate G = ni V / • ni is the intrinsic carrier concentration• V = active volume = lifetime (this is a function of the radiation damage, described by K)
• Surface damage effects• Ultimate limits not included in calculation
– Transmutation doping of active region– Tunneling– Extended defect generation (defect coalescence)
• References:– Radiation Effects in Advanced Semiconductor Materials and Devices by C. Claeys and E. Simoen, Springer Series
in Materials Science, 57, pp. 28 – 36, 132 – 138 (2002).– M. D. Osborne, P. R. Hobson, and S. J. Watts, “Numerical Simulation of Neutron Radiation Effects in Avalanche
Photodiodes,” IEEE Trans. Electron. Dev. 47(3), pp. 529 – 536 (2000).– N. Dharmarasu et al., “High-radiation-resistant InGaP, InGaAs, and InGaAs solar cells for multijunction solar cells,
“ Appl. Phys. Lett. 79(15), pp. 2399 – 2401.
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Radiation Damage
• Bulk defects: intrinsic materials property, accurate measurements
• Surface defects: depends on surface treatment:
– Si: SiO2 vs. Si3N4
– GaAs:
• Imperfect dielectric surface passivationvs. perfect single-crystal passivation
X
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Why is GaAs (GaInP) rad hard?
• Generation Rate: G = ni V /
• Radiation Damage: rad = 1/K
• G() ≈ ni V K
V = 1 mm 1 mm 1 µm
ni K G ()cps/mm2
Cell density
Silicon 1E10/cm3 0.10E-6 cm2/s 1.0E-3
GaAs 2E6/cm3 1.25E-6 cm2/s 2.5E-6
GaInP 300/cm3 1.25E-6 cm2/s 3.8E-10
9 Nov 2011 2727
Why is GaAs (GaInP) rad hard?
• Result for = 1E14/cm2 (SLHC Barrel max dose)
• Cell density assumes saturation rate per cell occurs for count rates > 1E6 cps
V = 1 mm 1 mm 1 µm
ni K G (1E14)cps/mm2
Silicon 1E10/cm3 0.10E-6 cm2/s 1.0E11
GaAs 2E6/cm3 1.25E-6 cm2/s 2.5E8
GaInP 300/cm3 1.25E-6 cm2/s 3.8E4
9 Nov 2011 2828
Why is GaAs (GaInP) rad hard?
• Result for = 1E14/cm2 (SLHC Barrel max dose)
V = 1 mm 1 mm 1 µm
ni K G (1E14)cps/mm2
Cell density
Silicon 1E10/cm3 0.10E-6 cm2/s 1.0E11 100K/mm2
GaAs 2E6/cm3 1.25E-6 cm2/s 2.5E8 250/mm2
GaInP 300/cm3 1.25E-6 cm2/s 3.8E4 < 1/mm2
9 Nov 2011 2929
Why is GaAs (GaInP) rad hard?
• Result for = 7E15/cm2 (SLHC Barrel max dose)
• Cell density assumes saturation rate per cell occurs for count rates > 1E6 cps
V = 1 mm 1 mm 1 µm* 7.0e12 cps/mm2 = 1 µA/mm2 gain
ni K G (7E15)cps/mm2
Cell density
Silicon 1E10/cm3 0.10E-6 cm2/s 7.0E12* 7M/mm2
GaAs 2E6/cm3 1.25E-6 cm2/s 1.8E10 18K/mm2
GaInP 300/cm3 1.25E-6 cm2/s 2.6E6 3/mm2