Fluence dependent recombination lifetime in neutron and proton irradiated MCz , FZ and epi-Si structures

E.Gaubas, J.Vaitkus, T.Čeponis, A.Uleckas, J.Raisanen, S.Vayrynen, and E.Fretwurst

Vilnius University, Institute of Materials Science and Applied ResearchHelsinki University, Accelerator Laboratory

University Hamburg

Outline

Objectives of investigations

Samples, irradiations and experiments

Fluence dependent lifetime variations

Characteristics of lifetime cross-sectional profiles

Summary

Objectives / investigations

- Direct measurements of recombination lifetime fluence dependences:

comparative analysis of carrier decay in MCZ, FZ and epi-Si neutron irradiated structures

- Control of possible anneal of defects:

heat treatments 80C

- Recombination lifetime variations with energy of protons

- Recombination characteristics in 2 MeV proton irradiated n-FZ Si

combined investigations of MWR, DLTS and RR in 2MeV proton irradiated structures

- Cross-sectional scans within structure depth to control defect production profiles

Samples

Structures tested

1.9 and 2.0 MeV protons

200µm60µm

n+-Sin-Siρ=0,04 Ωcmρ=25 Ωcm

Apšvitos srautas

Diodes

Wafer structures

=41-49 m

|2 MeV=7 m

Irradiation plan March 2007 TRIGA reactor Resp. Gregorarrival HH 15-06-2007, 12:20 in cold box

Material: Wacker FZ <111> 2 kOhmcm 290 µm Process STM W337

W337phi_n [cm-2] FZ

1.00E+13 B11

1.00E+13 E81.00E+14 Q51.00E+14 G131.00E+15 H21.00E+15 H31.00E+16 Q61.00E+16 I13

Irradiation TRIGA reactor November 2006arrival HH: 8. January 2007, by Gregor

Material: ITME p-EPI <111> 150 Ohmcm 50 µm Process: CIS

260868-01 annealingp-EPI 80 °C V_dep [V]

phi_n [cm-2] 50 µm t_max [days] at t_max

3.00E+13 16 31.3 88.11.00E+14 19 31.3 52.83.00E+14 27 31.3 47.91.00E+15 33 31.3 89.03.00E+15 36 31.3 268.01.00E+16 41 2.3 671.0

not irradiated 43* x xnot irradiated 44* x x* breakdown voltage about 60 V, guard ring not working

Irradiation TRIGA reactor March 2004

Material: ITME n-EPI <111> 50 Ohmcm 50 µm Process: CIS

6336-04 annealingn-EPI 80 °C V_dep [V]

phi_n [cm-2] 50 µm t_max [days] at t_max

2.00E+14 06 135.3 59.06.00E+14 08 135.3 3.21.00E+15 11 135.3 18.72.00E+15 17 135.3 90.94.00E+15 24 148.4 240.88.00E+15 28 135.3 450.01.00E+16 32 135.3 478.0

not irradiated 34 x xnot irradiated 35 x x

1

2

Neutron irradiated

Proton irradiated

FZ

n- epi

FZ n-Si

p- epi

WODEAN

VU-HUAL

Mesaurements: MW-PCD,RR, C-DLTS

M

Neutron fluence dependent recombination lifetime in FZ and epi- Si

1013

1014

1015

1016

100

101

102

103non-irradiated

Fluence (cm-2)

Neutron irradiated FZ diodes n-epi diodes p-epi diodes

(n

s)

Lifetime in neutron irradiated Si under heat treatments at 80C

1012 1013 1014 1015 101610-4

10-3

10-2

10-1

100

101

Okmetic MCZ<100> 1kcm as-irradiated

Heat treated at Tann= 800 C

for tanneal = 5 min 30 min 24 h Waker W337 FZ diodes- un-annealed

n-epi diodes 800 C-long anneal

p-epi diodes 800 C-long anneal

Re

com

bin

atio

n li

fetim

e (s

)

Neutron fluence (n/cm2)

Fluence dependent lifetime variations in different particle energy irradiated structures

1012

1013

1014

1015

1016

10-1

100

101

102

103

104

Neutron irradiated material MCZ as-irradiated

Proton irradiated material MCZ RT -50 MeV sFZ RT - 24 GeV/c DOFZ RT - 24 GeV/c V- n- FZ 2 MeV

R (n

s)

Fluence (cm-2

)

100 150 200 250 3000

20

40

60

80

100

120

140

V-cluster (S.Watts)

V2

-/0

V2

=/-

A (V-O)

FZ n-Si diode V

1.9 MeV protons 7x1012 p/cm2

FZ n-Si diode CERN-Oslo

5 MeV electrons 1012 e/cm2

DL

S (

a.u

.)

T (K)

0 2 4 6 8 10

10-2

10-1

100

101

irradiation spot effective radius

- V FZ n-Sienergy of protons 2 MeV

fluence 7*1013

p/cm2

(s

)

x (mm)

1.9 and 2.0 MeV protons

200µm60µm

n+-Sin-Siρ=0,04 Ωcmρ=25 Ωcm

Apšvitos srautas

Wafer structures

=41-49 m

20 mm

20 mmReff

Lateral lifetime variation

0 10 20 30 40 500

20

40

60

80

100

120

140

VVP Si Tomas`Proton energy 2 MeV

fluence 4*1014

p/cm2

(ns)

x (m)

MW-PCD-depth – scans

in 2 MeV protons irradiated FZ n-Si

0 10 20 30 40 500.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5V FZ n-Si Proton energy 2 MeV

fluence 4*1014 p/cm2

Am

plit

ude (

a.u

.)

x (m)

0 1 2 3 4 5 610

-3

10-2

10-1

100

UM

WR

(a.u

)

t s)

VVP Si TomoProton energy 2 MeV

fluence 4*1014

p/cm2

x = 40,0 m = 0,065 s = 1,1 s

200µm60µm

n+-Sin-Siρ=0,04 Ωcmρ=25 Ωcm

Apšvitos srautas

0.0 0.1 0.2 0.30

1

2

UM

WR

(a.u

)

t s)

VVP Si TomoProton energy 2 MeV

fluence 4*1014

p/cm2

x= 1 m x= 40 m

Cross-sectional scans within depth of neutron irradiated wafer

fiber

MW coaxial needle-tipantenna

sample

0 100 200 30010

0

101

102

103

MCZ 1 k·cm, d= 300 m neutron fluence

1012

cm-2

3·1014

cm-2

1015

cm-2

3·1015

cm-2

MWR amplitude R(n

s),

MW

R a

mpl

itude

(a.

u.)

Z (m)

Fluence dependent variations of

MW-PCD, DLTS and RR characteristics

in 2 MeV protons irradiated FZ n-Si

100 150 200 250 300

0,2

0,4

0,6

0,8

1,0

1,2cluster edge &/or H-?

V2

-/0

V2

=/-

V-O-?

non-irradiated2 MeV protons irradiated

7E12 p/cm2

7E13 p/cm2

7E14 p/cm2

DL

S (

a.u

.)

T (K)

1013 10140

400

800

1200

1600

2000

2 MeV protons

RR, n

s

, cm-2

IF=0.5A

IF=1A

IF=2A

IF=4A

IF=6A

IF=8A

IF=10A

1013

1014

1015

100

101

102

2 MeV protons FZ n-Si wafers/diodes

R (

ns)

Fluence (p/cm2)

SUMMARY

Lifetime decreases from few s to about of 200 ps with enhancement of neutron irradiation fluence ranging from 1012 to 31016 n/cm2, as measured directly by exploiting microwave probed photoconductivity transients and verified by dynamic grating technique.

Lifetime values are nearly the same for neutron irradiated wafer and diode samples. These values are close to that in >20 MeV proton irradiated various Si diodes.

Small increase of lifetime values under annealing can be implied.

Lifetime values are nearly invariable within wafer thickness for high energy neutrons, while the lifetime depth profile is inhomogeneous for 2 MeV protons irradiated structures.

Production of recombination defects in ~2 MeV protons irradiated FZ Si is efficient, and lifetime depth profiles correlate with stopping range of particles.

Thank You for attention!

Clusters

V2

V2

V2

V2

V2

V2

V2

V2

V2

V2

V2

V2 V

2

PD

V2 V

2

V2

V2

V2

V2

V2

V2

V2

V2

V2

V2 V

2

V2 V

2

V2

V2V

2 V2 V

2 V2 V

2

V2

V2

V2

V2 V

2 V2

V2

V2

V2

V2 V

2 V2 V

2

V2 V

2

V2 V

2

Fluence

Measurement techniques and instruments

Dynamic gratings (DG)

Diffraction efficiency (=I-1/I0) on light induced dynamic grating is a measure   (N)2 of excess carrier density, while its variations in time (t)  exp(-2t/G) by changing a grating spacing () enable one to evaluate directly the parameters of grating erase 1/G = 1/R + 1/D  through carrier recombination (R) and diffusion D = 2/(42D) with D as a carrier diffusion coefficient.

K.Jarasiunas, J.Vaitkus, E.Gaubas, et al. IEEE Journ. QE, QE-22, (1986) 1298.

Microwave probed photoconductivity (MW-PCD)

in MW reflection mode (MWR)

k

E

cw MW probe

laser lightpulsed excitation R

kk

E

cw MW probe

laser lightpulsed excitation R

MWR >100m 0 =(4/c )dc, transient:(t) (t) FC nexFC (t)

(t)

E.Gaubas. Lith. J. Phys., 43 (2003) 145.

Rload

MB tiltas

MW oscillatorwith adjustable power

and frequency

MB cirkulatorius

MB tiltas

MW circulator

f0.5 GHz,U1 mV/pdf0.5 GHz,U1 mV/pd

TDS-5104

Microchip laser STA-01

exc ~700 ps, Eexc 10 J

MW slitantenna

sample

MW bridge

Attenuatorof light density Sliding short

Sliding short

Sliding short

Amplifier (>50)

MW detector

Rload

MB tiltas

MW oscillatorwith adjustable power

and frequency

MB cirkulatorius

MB tiltas

MW circulator

f0.5 GHz,U1 mV/pdf0.5 GHz,U1 mV/pd

TDS-5104

Microchip laser STA-01

exc ~700 ps, Eexc 10 J

MW slitantenna

sample

MW bridge

Attenuatorof light density Sliding short

Sliding short

Sliding short

Amplifier (>50)

MW detector

MB tiltasMB tiltas

MW oscillatorwith adjustable power

and frequency

MW oscillatorwith adjustable power

and frequency

MB cirkulatorius

MB tiltas

MW circulator

f0.5 GHz,U1 mV/pdf0.5 GHz,U1 mV/pd

TDS-5104

Microchip laser STA-01

exc ~700 ps, Eexc 10 J

Microchip laser STA-01

exc ~700 ps, Eexc 10 J

MW slitantenna

sample

MW bridge

Attenuatorof light density Sliding short

Sliding short

Sliding short

Amplifier (>50)

MW detector

The microwave probed photoconductivity (MW-PCD) technique is based on the direct measurements of the carrier decay transients by employing MW absorption by excess free carriers. Carriers are photoexcited by 1062 nm light generated by pulsed (700 ps) laser and probed by 22 GHz cw microwave probe.

MW instruments at VU

Lateral mappingCross-sectional scan

Recombination lifetime in wafer and diode samples measured by MWR

1012 1013 1014 1015 1016

10-4

10-3

10-2

10-1

100

Okmetic MCZ<100> 1kOhm·cm 300 m MWR, CIS 8556- 14 wafers 1 - 63 passivated CIS 8556- 14 wafers measured by DG technique CIS 8556-01 diodes neutron irradiated

1/ R

(n

s-1)

Fluence (n/cm2)

1012 1013 1014 1015 101610-4

10-3

10-2

10-1

100

101

=1

Okmetic MCZ<100> 1kOhm·cm 300 m non-processed CISSamples 8556- 14 1 - 63 passivated wafers

- directly measured values &extracted from the decrease of amplitude UMWR

wafers 54-60 measured by DG

R

-1 (

ns-1)

Fluence (n/cm2)

Neutron fluence dependent recombination lifetime in MCZ Si

0 5 10 150

5

10

15

20

- H1-1012 n/cm2

-H61

- H2-1013 n/cm2

- H62

- H3-1014 n/cm2

- H63

- H4-3·1014

n/cm2

- H64

- H53-1015

n/cm2

- H54

- H55-3·1015

n/cm2

- H56

- H57-1016

n/cm2

- H58

- H59-3·1016

n/cm2

- H60

UM

WR (

a.u

.)

t (s)

R t|U ~ exp(-1)

R gexcRs/gexcRL (UMWRs<2 ns /UMWRL>5 ns)

1012 1013 1014 1015 1016

10-1

100

101

102

103

104

Laser pulse limit

Electr. circuitry limit

Okmetic MCZ<100> 1kOhm·cm 300 m non-processed CISSamples 8556- 14 1 - 63

- directly measured values - extracted from the decrease of amplitude U

MWR

Eff

ect

ive

life

time

(n

s)Neutron fluence (cm

-2)

Combined direct techniques