Solid State Physics Group Experimental Physics Dept. University … · 2003. 11. 18. · CdTe x-ray...

Ettore Vittone CERN, 3rd RD50 Workshop, 3-5.11.2003 1

ProjectsProjects“Diamond for ionizing radiation detection”, RD42-CERN collaboration and INFN"Research of charge transport properties in SiC by nuclear microprobe technique" project supported by NATO Science Programme“Silicon Carbide Radiation Detectors for Room and High Temperature Spectrometry”, COFIN-MIUR

• G.Bertuccio: Dept Elect Engn & Informat Sci, Politecnico of Milano• A.Cavallini: Physics Dept., University of Bologna• F.Nava: Physics Dept., University of Modena• C.Lanzieri:Alenia Marconi Systems, Roma (I)

Solid State Physics Group

Experimental Physics Dept. University of TorinoClaudio Manfredotti – Full professor

Ettore Vittone – Associated professor

Alessandro Lo Giudice – INFM researcher

Paolo Olivero – PhD student

Floriana Fasolo – PhD student


OUTLINEOUTLINE

• Introduction• Characterisation techniques:

– IBIC– IBIL– XBIC– XBIL

• Silicon Carbide characterisation• Radiation damage analysis• Neutron detection


IONISATION RADIATION micro-PROBES

Materials and devices

Si p-n junctions

CdTe x-ray detectors

GaAs Schottky diodes

Diamond radiation detectors

SiC Schottky diodes

Study of uniformity

Charge collection efficiency maps and profiles

Measurement of minority carrier diffusion length

Study of radiation induced damage

MeV ions keV x-raysIBIC - Charge collection efficiency - XBIC

IBIL - Radiation induced Luminescence - XBIL

Opto-electronic characterisation


Ion Beam AnalysisIon Beam AnalysisNuclear microprobe facility @

Ruđer Bošković Institute (Zagreb, Croatia)Dr. Milko Jaksic

•6 MV Tandem accelerator•available ions: H, C, Li, O, …•micrometric spot size•PIXE, IBICC measures

AN2000 microbeam facility @INFN National Laboratories (Legnaro ,I)

Dr. Valentino Rigato

2.5 MV Van de Graaff accelerator•available ions: H, He•micrometric spot size•PIXE, IBICC and IBIL measures•recently developed cryogenic apparatus


IBIC Set upIBIC Set up

frontal

lateral

Ion beam


0 20 40 60 80 100 1200

20

40

60

80

100

120

X Axis

Y A

xis

19.34 -- 20.84 17.84 -- 19.34 16.34 -- 17.84 14.84 -- 16.34 13.34 -- 14.84 11.84 -- 13.34 10.34 -- 11.84 8.840 -- 10.34 7.340 -- 8.840 5.840 -- 7.340

0 20 40 60 80 100 1200

20

40

60

80

100

120

X Axis

Y A

xis

87.10 -- 88.60 85.60 -- 87.10 84.10 -- 85.60 82.60 -- 84.10 81.10 -- 82.60 79.60 -- 81.10 78.10 -- 79.60 76.60 -- 78.10 75.10 -- 76.60 73.60 -- 75.10

0 20 40 60 80 100 1200

20

40

60

80

100

120

X Axis

Y A

xis

96.80 -- 98.30 95.30 -- 96.80 93.80 -- 95.30 92.30 -- 93.80 90.80 -- 92.30 89.30 -- 90.80 87.80 -- 89.30 86.30 -- 87.80 84.80 -- 86.30 83.30 -- 84.80

75 80 85 90 95 100 1050

500

1000

1500FRB L12, frontale230 V

Pixe

l

Efficiency (%)

65 70 75 80 85 90 950

1000

2000

FRB L12, frontale93 V

Pix

el

Efficiency (%)

0 5 10 15 20 25 300

500

1000

1500

2000 FRB L12, frontale30 V

Pixe

l

Efficiency (%)

FRBBL12

C = 3x1014 cm-3

2 mm

1 cm

pre-amplifierSchottky contact

ohmic contact

(frontal irradiation)2 MeV protonmicrobeam

0.1

mm GaAs

(back irradiation)2 MeV protonmicrobeam

sample holder

active region

lateral IBIC2.4 MeV proton

microbeam

2 mm

1 cm

2 mm

1 cm

pre-amplifierSchottky contact

ohmic contact

(frontal irradiation)2 MeV protonmicrobeam

0.1

mm GaAs

(back irradiation)2 MeV protonmicrobeam

sample holder

active region

lateral IBIC2.4 MeV proton

microbeam

GaAs Schottky diodes


LATERAL IBICC; 2.4 MeV protons

40 60 80 100 120 140 160 180 200 220 240 2600,0

0,2

0,4

0,6

0,8

1,0

GaAs SL69-CT n.1LNL 14/16 Aprile 1998; Protoni 2.4 MeV

183 V 132 V 83 V

35 V

Effi

cien

za

Posizione (µm) 10 20 30 40 50 60 70 80 90100 20010

20

30

40

5060708090

100

200

GaAs SL69-CTLNL 14/16 Aprile 1998; Protons 2.4 MeV

Width = a*(bias)^bChi^2 = 0.7861a 1.15593 ±0.32994b 0.95314 ±0.05655

Dep

letio

n la

yer w

idth

(µm

)

Bias Voltage (V)

0 24 49 73 98 122 146 171 195 2200

24

49

73

98

122

146

171

195

220

244

268

V=+83

0 24 49 73 98 122 146 171 195 2200

24

49

73

98

122

146

171

195

220V=+35

0 24 49 73 98 122 146 171 195 2200

24

49

73

98

122

146

171

195

220

SchottkyBarrier

SchottkyBarrier

V=+132

1.0006.00011.0016.0021.0026.0031.0036.0041.0046.0051.0056.0061.0066.0071.0076.00

0 24 49 73 98 122 146 171 195 2200

24

49

73

98

122

146

171

195

220

100 µm

efficiency %

V=+183

GaAs

active region

Schottky contact

GaAs2.4 MeV H+

Ohmic contact


HAMAMATSU R376 fused silica window

(160-850 nm).

1200 l/mm blazed at 500 nm, spectral range 300-900 nm

Cathodoluminescence (CL) and Ionoluminescence (IL) Mono CL2 system by Oxford Instruments (F=30 cm, aperture=F/4.2)


High irradiation dose produce damage.

In diamond it is possible to observe an intensity decrease of band A and 615 nm peak.

Also there is a 510 nm H3 centre creation.

( ) ( )DDII ⋅⋅−⋅⋅=−⋅= −1570 1012.1exp1091.1exp σ

0 1x1015 2x1015 3x1015 4x1015 5x10150,0

2,0x106

4,0x106

6,0x106

8,0x106

1,0x107

1,2x107

1,4x107

1,6x107

1,8x107

433

nm p

eak

area

[a.u

.]

Dose [Protons/cm2]

Experimental

First order exponential decay fit of data

Band A decay in sample CM1

300 400 500 600 700101

102

103

104

105

106

Scan1 Scan2 Scan3 Scan4 Scan5 Scan6

Cou

nts

[a.u

.]

Wavelenght [nm]

Sample: CM1

300 400 500 600 700101

102

103

104

105

106

Scan1 Scan2 Scan3 Scan4 Scan5 Scan6

Cou

nts

[a.u

.]

Wavelenght [nm]

Sample: R117

Proton damage in Proton damage in diamonddiamond


• hνX-ray = 2.5 ÷ 8 keV• synchrotron source• submicrometric spot size• XBICC, XBIL measures

ID21 X-ray microscopy beamline @European Synchrotron Radiation Facility

(Grenoble, France)Dr. R.Barrett and R.Tucoulou

XX--ray analysisray analysis

X

Y Z

Sample

Vbias

Electrode

Keithley 617picoamperometer

OndulatorCrystal

monochromatorZone plate

objective lens

Aperture Raster X-Ypiezo scanner

8

V (0-2 V)

ν (0-100 kHz)

∫ signal(# counts)

APMT

V → νX-ray µbeam

V (0-2 V)

ν (0-100 kHz)

∫ signal(# counts)

APMT

V → νX-ray µbeam


XBICC on diamondXBICC on diamond

XBICC map on diamond: the circular electrode is clearly visible; the black spot is the contacting silver drop; note the polycrystals (invisible to optical microscope)

Zooms (90x100 µm2) : “electronic” crystals are clearly visible, with sizes depending from the applied voltage


Silicon carbideSilicon carbide

Silicon carbide samples:• n-doped 4H-SiC epitaxial layers on n+-doped SiC substrates by CREE• gold Schottky contacts + guard rings by Alenia Marconi• ohmic T-Pt-Au contacts by Alenia Marconi

Ohmic contact - Ti/Pt/Au

n+, 4H – SiC, 360 µm

substrate

n, 4H – SiC, 40 ± 2 µm epitaxial 4H-SiC

circular Schottky contactNi2Si φ = 1.5 mm

Si-face

C-face

sample section schematics

The Schottky contacts have been formed on the silicon surface of the epitaxial layer by deposition of a thin Au film, 100 nm thick. Ti/Pt/Au metallization system was used to realise the ohmic contacts on the whole carbon back surface.The metallizations were obtained by e-beam deposition in high vacuum (10-7 torr) and no heat treatment was performed after metallization.


Schottky PotentialVbi=(0.959±0.007) V

Constant Doping DensityNd=(4.52±0.03)·1014

atoms/cm3

Ideality Factorη=(1.153±0.003)


SiC sample IKZ P2220

Ohmic contact - Ti/Pt/Au

n+, 4H – SiC, 360 µm

substrate

n, 4H – SiC, 40 ± 2 µmepitaxial 4H-SiC

circular Schottky contactNi2Si φ = 1.5 mm Si-

face

C-face

Epitaxial layer (Institut für Kristallzuchtung of Berlin): N doping (from 4.7x1013 to 7.7x1013cm-3), 40 µm thick

Substrate (CREE): n+ doping (>1018 cm-3), 360 µm

Schottky contact + guard ring (Alenia Marconi): Ni2Si; 356 nm thick

Ohmic contact(Alenia Marconi): Ti-Pt-Au

F.Nava et at., to be published in NIMB

4H-SiC epitaxial layers grown at the Institut für Kristallzüchtung (Berlin) on 4H-SiC substrates by CREE


0 50 100 150 200 250 300 350 400 45010-11

10-10

10-9C

UR

REN

T D

ENSI

TY (A

/cm

2 )

REVERSE BIAS (V)

0 10 20 30 40 500

5

10

15

20

25

30

35

40

Dep

letio

n re

gion

wid

th (µ

m)

Bias Voltage (V)

0 5 10 15 204

5

6

7

8

9 4H-SiC #G

N(X

)[x10-1

3cm

-3]

X [µm]

Schottky Barrier height : 1.84 eV

Ideality factor:1.05


X

Y Z

Sample

Vbias

Electrode

Keithley 617picoamperometer

OndulatorCrystal

monochromatorZone plate

objective lens

Aperture Raster X-Ypiezo scanner

ID21 scanning x-ray microscope (SXM)ESRF - Grenoble (F)

3 keV x-ray energy; about 10 photons/s;8

Spot size about 1 mµAttenuation length in SiC: 4 mAu contact (100 nm thick): attenuation 33%

µ


XBICC on silicon carbideXBICC on silicon carbideXBICC maps

circular electrode

silver drop

zoom region


XBICC on silicon carbideXBICC on silicon carbideXBICC maps

At 0 V bias voltage point defects (micropipes?) are clearly visible, which disappear at higher bias voltages.


3.0 3.2 3.4 3.6 3.80

50

100

150

Photocurrent (a.u.)

BIAS = 0 Vab_02

Pix

els

3.0 3.2 3.4 3.6 3.80

50

100

150 BIAS = 50 Vab_08

Pixe

ls

0.0 -0.2 -0.4 -0.6 -0.8 -1.0 -1.2 -1.4 -1.60.0

-0.2

-0.4

-0.6

-0.8

-1.0

-1.2

-1.4

-1.6Bias = 50 V

PhotoCurrent

X Axis (mm)

Y Ax

is (m

m)

3.1503.1603.1703.1793.1893.1993.2093.2193.2283.2383.2483.2583.2683.2773.2873.2973.3073.3173.3263.3363.3463.3563.3663.3753.3853.3953.4053.4153.4253.4343.4443.4543.4643.4743.4833.4933.5033.5133.5233.5323.5423.5523.5623.5723.5813.5913.6013.6113.6213.6303.6403.650

A

C

D B

0.0 -0.2 -0.4 -0.6 -0.8 -1.0 -1.2 -1.4 -1.60.0

-0.2

-0.4

-0.6

-0.8

-1.0

-1.2

-1.4

-1.6

PhotoCurrent

Bias = 0 V

X Axis (mm)

Y Ax

is (m

m)

3.1503.1603.1703.1793.1893.1993.2093.2193.2283.2383.2483.2583.2683.2773.2873.2973.3073.3173.3263.3363.3463.3563.3663.3753.3853.3953.4053.4153.4253.4343.4443.4543.4643.4743.4833.4933.5033.5133.5233.5323.5423.5523.5623.5723.5813.5913.6013.6113.6213.6303.6403.650

D

CB

A

P2220; from IfK

XBIC, ESRF


0.0 -0.2 -0.4 -0.6 -0.8 -1.0 -1.2 -1.4 -1.60.0

-0.2

-0.4

-0.6

-0.8

-1.0

-1.2

-1.4

-1.6

PhotoCurrent

Bias = 0 V

X Axis (mm)

Y Ax

is (m

m)

3.1503.1603.1703.1793.1893.1993.2093.2193.2283.2383.2483.2583.2683.2773.2873.2973.3073.3173.3263.3363.3463.3563.3663.3753.3853.3953.4053.4153.4253.4343.4443.4543.4643.4743.4833.4933.5033.5133.5233.5323.5423.5523.5623.5723.5813.5913.6013.6113.6213.6303.6403.650

D

CB

A

0 5 10 15 20 25 300

100

200

300

400

Pixe

ls

Photocurrent (A.U.)

10 20 30 40 50 60 70 80 90 100

10

20

30

40

50

60

70

80

90

100

V = -50 V

X Axis (µm)

Y A

xis (µm

)

23.0023.6924.3825.0625.7526.4427.1327.8128.5029.1929.8830.5631.2531.9432.6333.3134.00


X-Y Scanning system

Quadrupole focussing lenses

Sample holder

Analysis chamber

Sample

Vbias

Charge sensitivepre-amplifier

Amplifier

Electrode

X

Z

XY

IonBeam

Nuclear Microprobe at the Laboratory forIon Beam Interactions

Rudjer Boskovic Institute , Zagreb (HR)

H, Li, C, O

Ion Beam Induced Charge Collection Microscopy


0 200 400 600 800 1000 1200 1400 1600 1800 20000

200

400

600

800

1000

1200

1400

Noise

Peak #2

Peak #1

Test signal (pulser)

coun

ts

channel

Peak #1 map Peak #2 map

Vbias = 75 V

4H-SiC IKZ sample1.5 MeV protons


0 5 10 15 20 25

25

50

75

100

0.7 MeV


0.9 MeV

0 5 10 15 20 25

25

50

75

100


1.1 MeV

0 5 10 15 20 25

25

50

75

100


1.3 MeV

0 5 10 15 20 25

25

50

75

100


1.5 MeV

0 5 10 15 20 25

25

50

75

100


0 5 10 15 20 25

25

50

75

100

1.7 MeV


0 5 10 15 20 25

25

50

75

100

1.7 MeV

radiation damage (surface)

contact scratches (surface)

defects ? (depth)0.7 MeV


[ ]

potential weightedV

E(r)

velocity; hole(r)v ion;concentrat h)r;t'p(r,equation continuity holes the for function sGreen' the is

holes from Induced Charge thetheorem, Gunn-Ramo-Schockleythe From

Vi

p0

=∂∂

==

∂∂⋅⋅−= ∫ ∫

Ω

ole

V)r(E)r(v)r;'t,r(prd'dtq)t(Q

Vip0

t

0in

The continuity equation involves linear operators

The charge induced from holes can be evaluated by solving a single, time dependent adjoint equation.

( )p

p*

p0ppGpDp

tp

τ−+∇⋅+⋅φ∇⋅µ+⋅∇+=

∂∂ +

+++ rrr

ipp

in

VEG

Qp

∂∂

⋅φ∇⋅µ=

=

+

+

E.Vittone, IBA2003 conf., to be published in NIMB


−=+

Lxexp)x(p

Considering

-a one dimensional problem limited to the neutral region

-an infinite device thickness

-constant transport parameters (µ,τ)

The Green’s function of the continuiity equation, i.e. the solution of the adjoint equation for t→∞ is

p+ is the total charge induced at the sensing electrode by a moving charge generated at a distance x from the border of the neutral region.


Collected Charge ∫ ∫

−−⋅

+

=

W d

W pBSiCBSiCtot dx

LWxexp

dxdEdx

dxdEQ

0

11εε

DRIFT

Drift+Diffusion Model

BRAGG CURVE

(SRIM 2000)

BdxdE

Approximations

• Abrupt Junction

• Infinite semiconductor

DIFFUSION

∫

−−⋅

d

)V(W pB

dxL

)V(WxexpdxdE∫

)(

0

VW

B

dxdxdE

5.48 MeV He++


βεε b

SiSiC ⋅=

0 1 2 3 4 8 12 16 200

100

200

300

400

500

600

700

800

Depletion Layer

Width @

150 V

Energy Loss of He++ ions in SiCElectrode: 100 nm, Au

1.0 MeV He++ 1.5 MeV He++ 2.0 MeV He++ 5.48 MeV He++

Ener

gy L

oss

(keV

/um

)

Depth (µm)

Sample RUN1D3 (CREE): εSiC=(7.8±0.1) eVfrom He++ measurements

Sample SiCP2220 (IfK): εSiC=(7.5±0.1) eV from He++ measurements

Sample SiCP2220 (IfK): εSiC=(7.7±0.1) eV from H+ measurements

100% CCE in the depletion regionPlasma EffectsElectrode absorption

Fixed voltageFixed voltage; ; Variable Ion EnergyVariable Ion Energy


Run1D5

1.5 MeV H+

100 150 200 250 300 3500

10

20

30

40

50

coun

ts

channel

V=250 V

V=150 VV=90 VV=50 VV=10 VV=0 V

FWHM

40 keV

FWHM about 40 keV

V=50 V

V=100 V V=250 V

Fixed energyFixed energy; ; Variable voltageVariable voltage

Run1D3241Am α source

E=5.48 MeV


IBICC on silicon carbideIBICC on silicon carbidedetermination of hole diffusion length

Lh ≈ 5.8 µm Lh ≈ 8.6 µm

“Run1D3” sample, 5.48 MeV He “Run1D5” sample, 1.5 MeV H

⇓ ⇓τh ≈ 113 ns τh ≈ 247 nsif µh ≈ 115 V cm-2 s-1

is assumed


0 5 10 15 20 25 30 35 400

10

20

30

40

50

60

70

80

90

100

a)

Lp = 10.5 µmCC

E (%

)

REVERSE BIAS (V)

CCE-exp.CCE-driftCCE-diffusionCCE-theory

0 5 10 15 20 25 30 35 400

10

20

30

40

50

60

70

80

90

100

b)

Lp = 4.85 µm

CC

E (%

)

REVERSE BIAS (V)

Best WorstSiC sample IKZ P2220

F. Nava*, G. WagnerÄ, C. Lanzieri<, P. Vanni*, E. Vittone¨. “Investigation of Ni/4H-SiCdiodes as radiation detectors with low doped n-type 4H-SiC epilayers”, NIM B (2003)


0 50 100 1500 50 100 1500

10

20

30

40

50

60

70

80

90

100

0 20 40 60 80 1000

10

20

30

40

50

60

70

80

90

100

He++ 4.14 MeV

REVERSE BIAS (V)

experimental theoretical fit drift only diffusion only

CC

E (%

)

He++ 5.48 MeV

REVERSE BIAS (V)

He++ 2.00 MeV

REVERSE BIAS (V)

0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 1,110-15

10-14

10-13

10-12

10-11

10-10

10-9

10-8

10-7

10-6

10-5

10-4

10-3

a)

# fluence (p/cm2)

0 9.37x1013

Proton Irradiated 4H-SiC

CU

RR

ENT

(A)

FORWARD BIAS (V)

0 40 80 120 160 20010-13

10-12

10-11

10-10

10-9

10-8

b)

Proton Irradiated 4H-SiC

# fluence (p/cm2)

0 9.37x1013

CU

RR

ENT

(A)

REVERSE BIAS (V)

F.Nava, E.Vittone, P.Vanni, G.Verzellesi, P.G.Fuochi, C.Lanzieri, M.Glaser, “Radiation Tolerance of epitaxial Silicon Carbide detectors for electrons, protons and γ –rays”,NIM A 505 (2003), 645

24 GeV/c proton irradiation @ 26°C

at the CERN-Proton Synchrotron

Fluence = 1.43x1013 protons/cm2

-6 -5 -4 -3 -2 -1 0 1 20

1x1016

2x1016

3x1016

4x1016

5x1016

6x1016

7x1016

8x1016

9x1016

1x1017

x

0 9.37 1013

# fluence (p/cm2)

Proton irradiated 4H - SiC

(Cap

acita

nce/

Area

)-2 (F

/cm

2 )-2

BIAS (V)


0 50 100 150 200 2500,0

0,2

0,4

0,6

0,8

1,0

0 50 100 150 200 2500,0

0,2

0,4

0,6

0,8

1,0

0 50 100 150 200 2500,0

0,2

0,4

0,6

0,8

1,0

0 50 100 150 200 2500,0

0,2

0,4

0,6

0,8

1,0

CC

E

Φ=1.03 eVcc=0.7 µm/V1/2

L=9.5 µm

Bias voltage (V)

CC

EΦ=1.13 eVcc=0.8 µm/V1/2

L=1 µm

20 Mrad

Bias voltage (V)

2 Mrad

CC

E

Φ=1.06 eVcc=0.8 µm/V1/2

L=2 µm

Bias voltage (V)

8.2 MeV electron 0 Mrad 2 Mrad 20 Mrad 40 Mrad

He++ 4.14 MeV

CC

E

Bias voltage (V)

8.2 8.2 MeV electrons MeV electrons at ISOFat ISOF--CNR lab. CNR lab.



0 40 80 120 160 200 240 280 3200

20

40

60

80

100

120

# Dose (Mrad) 0 2 10 20 40

4.14 - MeV alpha

60Co Gamma Irradiated 4H-SiC,

CC

E (%

)

REVERSE BIAS (V)

60Co Gamma at ISOF-CNR


0 50 100 150 200 250

20

40

60

80

100

20

40

60

80

100

20

40

60

80

100

0 Mrad

Lp = 9.9 µmτp = 329.0 ns

a)

CC

E (%

) C

CE

(%)

CC

E (%

)

REVERSE BIAS (V)

c)

40 Mrad

Lp = 1.6 µmτp = 8.4 ns

2 Mrad

Lp = 5.0 µmτp = 84.4 ns

b)


Electrical spectroscopy Ion spectroscopy

Sample Neff

(cm3)Φ

(eV)

n Hole diffusion length

(µm)

Virgin 2.18E15 1.7 1.19 8.57

Proton irradiated

1014 p/cm2

1.43E15 1.72 1.18 1.0

Virgin 2.49E15 1.03 1.04 9.5

Electron irradiated

2 Mrad

2.69E15 1.06 1.04 2

Electron irradiated

20 Mrad

1.67E15 1.13 1.036 1

Virgin 2.49E15 1.03 1.034 9.9

Gamma irradiated

2 Mrad

2.28E15 1.03 1.033 5

Gamma irradiated

40 Mrad

2.21E15 1.03 1.034 1.6



IBICC on silicon carbideIBICC on silicon carbideIBICC maps – 2.0 MeV H+ induced damage

Consecutive IBIC scans ⇒ Charge collection efficiency as a function of adsorbed dose.

damaged region


0ppDp

p =τ

−∆⋅+

+

Hole adjoint continuity equation in the neutral region

Boundary conditions: p+(x=W)=1; p+(x=d)=0

)x(VK)x(N where)x(NvNv

1 irrirr

thirro

thop Φ⋅⋅=

⋅⋅σ+⋅⋅σ=τ

Nirr(x)= trap density

K = trap/vacancy

V(x) = Vacancy density/ion (vacancy/ion/cm)

F = fluence (ions/cm2/s)

5 10 15 20 25 30 35 40 45 500

1

2

3

4

5

6

7

8

Depth (um)

Vaca

ncy/

Ion/

um

SRIM2000 simulation

Vacancy/ion profileTotal Target Vacancies = 24 /Ion


charge drift charge diffusion

0 5 10 15 20 25 30 35 40 45 500

50

100

150

dW0

Depl

etio

n la

yer

Ener

gy lo

ss (k

eV/µ

m)

Depth (µm)

∫ ∫ +⋅

ε+

ε=

W

0

d

W BSiCBSiCtot dx)x(p

dxdE1dx

dxdE1Q


Hole diffusion length profile Hole induced charge profile

K ⋅ σirr⋅vth=2.8x105 cm3/s

Assuming

σirr=10-13cm2 and vth=107cm/s

K=0.28 traps/vacancy

Since

About 24 vacancy/ion -> 6-7 traps/ion

0 10 20 30 40 500

1

2

3

4

5

6

7

8

9

Depth (um)

L (u

m)

0 10 20 30 40 5010-10

10-8

10-6

10-4

10-2

100

Depth (um)

p+ (u

m)

Φ=0

Φ=108 cm2 s-1

Φ=109 cm2 s-1

Φ=1010 cm2 s-1

Φ=4x1010 cm2 s-1

1 10 100100

110

120

130

140

150

160

170

Data: dann_DModel: user8 Chi^2/DoF = 0.61317R^2 = 0.99853 alfa 0.27968 ±0.00562coeffang 370.7071 ±1.30944termnot 22.96335 ±0.53554

Cha

nnel

Fluence (ions/cm2)


AmBe Neutron Source @ JRC IspraActivity: 3.6x107 neutrons/s

Fast neutron detection

circular Schottky contactAu (1000 Å), Φ = 2 mm

Si-face

C-face, Ohmic contact

Plexigas6LiF

4H-SiC


Fast neutron detection6Li Converter: Reaction 6Li(n,α)3H

Neutron cross section from LANL laboratory web site: http://t2.lanl.gov

Q-value of the (n,α) reaction: 4.78 MeV

Activity: 600 GBq

3.6·107 neutroni/s

No radiation damage was detected after an irradiation of about 109 neutron/cm2.


C cross sections

Elastic

12C(n,α)9Be

Si cross sections

28Si(n,α)25Mg

Elastic


Exposure @ the TAPIRO reactor at the ENEA Casaccia Center (Rome)

Giancarlo Rosi

10-2 10-1 100 101 102 1x103 104 1x105 106 1070

1x108

2x108

3x108

Neu

tron

flux

[cm

-2 s

-1]

En [eV]

The nominal power i 5 kW and the neutron flux is 4x1012 cm-2s-1 at the core center.

The irradiation was performed using an epithermal column.

Reactor power = 5 W or 10 W

Neutron flux: about 1-2x106 n cm-2s-1


Plexigas6LiF

IkZ_U3 4H-SiC

0 250 500 750 1000 1250 1500 1750 20000

2

4

6

8

10

12

14

16

Bias voltage = 2 V

Cou

nts

Energy [keV]

Reactor power = 10 WNeutron flux=2.3x106 n cm-2s-1

Acquisition = 900 sNeutron fluence = 2x109 n cm-2

3.6 cm thick moderator10-2 10-1 100 101 102 1x103 104 1x105 106 107

2x102

2x103

2x104

2x105

Torino, 11/10/03 MCNP4B simulationNeutron source: Tapiro reactor @ Power (10 W)Neutron flux behind LiF; Real geometry

without moderator with 3.6 cm polyethilene

Neu

tron

flux

[cm

-2 s

-1]

En [eV]

4He =2.05 MeV 3H =2.73 MeV0.2% counting efficiency

No counting and charge collection efficiency decrease after 3.7*1010 neutroni/cm2


CONCLUSIONSCONCLUSIONS

• Uniformity analysis IBIC-XBIC• “Definition of measurement scheme and

parameters necessary to extract for device modelling”

• Radiation damage• 4H-SiC Schottky diodes for neutron detection;

MCNP simulation


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Solid State Physics Group Experimental Physics Dept. University … · 2003. 11. 18. · CdTe x-ray...

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