Displacement Damage Mechanism and Effects - Swiss Space...

Space Radiation and its Effects on EEE Components

EPFL Space Center 9th June 2009

Displacement DamageMechanism and Effects

Christian PoiveyGordon Hopkinson



Outline

• Introduction• Mechanism• NIEL concept

– Terms and units• Effect of Defects• Device Effects, examples• System Level Effects• Bibliography



Introduction

• Semiconductor materials (Si, GaAs,..) are usually crystalline

• Space environment consists of energetic particles which can pass through shielding

• Leads to disruption in the lattice structure and device damage– Damage degrades electrical performances of

the device



Displacement DamageVacancies and interstitials migrate, either recombine ( ~90%)or migrate and form stable defects (Frenkel pair)

I

V VStable Defect



Displacement Damage• Energy of recoils (PKA spectrum) is

determined by the collision kinematics• electrons produce low energy PKAs• low energy protons (< 10 MeV in Si, higher in GaAs) : Coulomb (Rutherford) scattering dominates

• low energy PKAs

• neutrons and higher energy protons - nuclear elastic scattering and nuclear reactions (inelastic scattering)

• flat PKA spectrum

• above ~ 20 MeV in silicon, inelastic collisions tend to dominate

isolated (point) defects

cascades & multiple cascades

E

E



Cascades

After Johnston, NSREC short course 2000

•50 keV PKA is typical of what can be produced by a 1MeV neutron or high energy proton•Threshold displacement energy in Si: 21 eV



Non Ionizing Energy Loss (NIEL)

• Final concentration of defects depends only on NIEL (total energy that goes into displacements, about 0.1% of total energy loss) and not on the type an initial energy of the particle– Number of displacements (I-V pairs) is proportional to

PKA energy • Kinchin-Pease: N=T/2TD; T: PKA energy; TD: threshold energy to

create a Frenkel pair)

– In cascade regime the nature of the damage does not change with particle energy- just get more cascades

• nature of damage independent of PKA energy



Non Ionizing Energy Loss (NIEL)• Assume underlying electrical effect

proportional to defect concentration (Shockley Read Hall theory)– Damage constant depends on device and parameter measured

damage = kdamage x displacement damage dose

dEdE

EdENIEL∫)()( φ



Terms and Units• NIEL (displacement kerma = Kinetic Energy Released to

MAtter)– keVcm2/g or MeVcm2/g

• displacement damage dose DDD

DDD=∫NIEL(E)dΦ(E)dE (keV/g or MeV/g)dE

• Displacement damage equivalent fluence DDEF(monoenergetic beam)

FE0=∫(NIEL(E) dΦ(E)dENIEL(E0) dE

– e.g. 10 MeV protons/cm2 or 1 MeV neutrons/cm2



NIEL - Silicon

0.01

0.1

1

10

100

1000

0.1 1 10 100 1000Particle Energy (MeV)

NIEL

, (ke

Vcm

2/g)

Dale et al.Huhtinen and ArnioAkkerman et al.JunVasilescu & LindstroemASTM E 722Summers et al.Akkerman et al.

Electrons

Protons

Neutrons

Protons

Neutrons

Electrons

Si



NIEL - GaAs

0.001

0.01

0.1

1

10

100

1000

0.1 1 10 100 1000Energy (MeV)

NIE

L (k

eVcm

2 /g)

Summers et al.Akkerman et al.Summers et al.Akkerman et al.Akkerman et al.ASTM E 722

GaAs

Protons

Neutrons

Electrons



Effect of Defects

Also: scattering at defects reduces carrier mobility, but only at vey high fluences

GenerationValence Band

CompensationTrappingRecombination Tunneling

EDONOR

Et

Conduction Band

EC

EV

Leakage Current

Minority CarrierLifetime

CTE in CCDsalso

Carrier Removal

Carrier Removal

Leakage Currentespecially if narrow bangap

and high electric field



Device Effects – Lifetime Damage• Minority carrier lifetime

– affects bipolar ICs (e.g. wide base regions in lateral & substrate pnp transistors, >3 1010 50 MeV p/cm2)

– reduces detector responsivity (decrease in diffusion length, (Dτ)1/2)– reduces efficiency of solar cells– reduces light output of LEDs (non-radiative recombination)– threshold current increase in laser diodes– reduction of current transfer ratio (CTR) in optocouplers

• LED, phototransistor and coupling medium can be affected– sensitive devices can degrade at 1010 - 1011 50 MeV protons/cm2

Kφ

ττ+=

0

11



Device Effects – Majority Carrier Removal• approximate carrier removal rates

• effect depends on doping (and whether n- or p- type)• for doping of 1015/cm3, carrier removal starts to be important for 50

MeV proton fluences ~ 1012 p/cm2

• but lightly doped structures can degrade at lower fluence (e.g. i-region of a p-i-n diode: due to leakage currents - 1010 p/cm2)

– but p-i-n diodes harder than conventional diodes since not sensitive to lifetime effects - collection by drift rather than diffusion

• type inversion (n- to p-type) in detectors & increase in depletion voltage

• carrier removal important for solar cells at high fluence

Particle Silicon GaAs

1 MeV 0.15/cm 0.6/cmelectrons

50 MeV 12/cm 30/cmprotons



Device Effect - SummaryTechnology category sub-category Effects

General bipolar BJT hFE degradation in BJTs, particularly for low-current conditions (PNP devices more sensitive to DD than NPN)

diodes Increased leakage currentincreased forward voltage drop

Electro-optic sensors CCDs CTE degradation, Increased dark current, Increased hot spots, Increased bright columnsRandom telegraph signals

APS Increased dark current, Increased hot spots, Random telegraph signalsReduced responsivity

Photo diodes Reduced photocurrentsIncreased dark currents

Photo transistors hFE degradation??Reduced responsivity??Increased dark currents??

Light-emitting diodes LEDs (general) Reduced light power output

Laser diodes Reduced light power outputIncreased threshold current

Opto-couplers Reduced current transfer ratio

Solar cells SiliconGaAs, InP etc

Reduced short-circuit currentReduced open-circuit voltageReduced maximum power

Optical materials Alkali halidesSilica

Reduced transmission



Device Effects - Examples

Rax et al. IEEE Trans.Nucl. Sci. vol 46(6), pp. 1660-1665, 1999

Voltage Regulator



0.00

0.20

0.40

0.60

0.80

1.00

1.20

0.E+00 2.E+10 4.E+10 6.E+10 8.E+10 1.E+11

Fluence (32 MeV protons/cm2)

CTR

0/CTR

#20 initial CTR=98

#29 initial CTR=81

#49 initial CTR=54

Mitel 3C91C (device is made no coupling medium)

5mA drive Vce=5V

Device Effects, Example

Reed et al. IEEE Trans. Nucl. Sci. vol 48(6), pp. 2202-2209, 2001

Optocoupler



Device Effects - ExamplesLED

Johnston NSREC200 Short CourseNotes



Device Effects - Examples

CCDDark Image:

dark spikes& CTI damage

1.8E10 10 MeV p/cm2



Materials Effects• Effects in materials (insulators, optical glasses,

biological samples) are usually considered to be dominated by ionization processes– only a small fraction of the particle energy goes into

displacements– materials like insulators and glasses are disordered with no well

defined crystal structure (will contain many defects before irradiation)

– However displacement damage effects cannot be ruled out, particularly at the end of the particle track

• Displacement damage effects in photonic crystals tend to occur only at very high fluences



Photonic Crystal



NIEL deviations: GaAs devices

But NIEL scaling is a good first approximationremoves most of the energy (and particle) dependencewithout it, testing/prediction would be much more complicated

Walters et al., IEEE Trans. Nucl. Sci., vol. 48, pp 1773-1777, 2001



System Level Effects• Sensor degradation important for payloads

and star trackers– but usually a gradual change in performance

• but difficult to calibrate (e.g. RTS and CTI effects in CCDs)• CTI effects for Chandra CCDs

• Optocouplers have failed in space applications– Topex Poseidon, failures in optocouplers in thruster

monitoring circuits at 2 x 1010 p/cm2

– optocouplers used in many types of circuit (e.g. DC-DC converters)

• Solar cell degradation or failure



Bibliography• RADECS short course notes

– 2003 Gordon HopkinsonRadiation Engineering Methods for Space Applications, part 3B: Radiation Effects and Analysis, Displacement Damage

• IEEE NSREC short course notes– 1999 Cheryl Marshall

Proton Effects and Test Issues for Satellite Designers, Part B: Displacement Effects

– 2000 Allan JohnstonOptoelectronic Devices with Complex Failure Modes

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