Sb doped Ge - Agenda (Indico) · 2019. 9. 25. · 1 n-type high doping of Ge by Sb deposition and...

1

n-type high doping of Ge by Sb deposition and pulsed laser melting

Carraro ChiaraPhD student Physics – Univ. Of Padova

[email protected]

4th Position Sensitive Germanium Detectors and Application Workshop (PSeGe)

16-19 Semptember 2019 – INFN LNL

16/9/2019

Ge-based devices

2

Solar cells

Photodetectors

Plasmonic molecularsensors

Lasers

Nanolectronics

γ-Ray detectors

[email protected] – 4th PSeGe Workshop16/9/2019

Ge hot topics

3

𝜔𝜔𝑝𝑝 ∝𝑛𝑛𝑚𝑚∗

n-type heavy doping

Strain engineering


Ge-based devices

4

Solar cells

Photodetectors

Plasmonic molecularsensors

Lasers

Nanolectronics

γ-Ray detectors


Issues on Ge n-type doping Low active concentrations

N < solid solubility

(V. I. Fistul, CRC press 2004)

(A ChroneosAPR 2014)

High Diffusivities

Ion ImplantationDamage

Ge implanted with 50 KeV 6×1015 Sb/𝑐𝑐𝑚𝑚2(Bruno JAP 2010)

[email protected] – 4th PSeGe Workshop16/9/2019 5

Sb deposition + PLM

6

Sb

Ge substrate

Sb Sputtering (1 – 8 nm) Sb RTP Evaporation(self-limited monolayer deposition)

Pulsed Laser Meltingfor dopant diffusion, incorporation, and activation

• Nd-YAG 𝜆𝜆=355 nm, 7 ns, 400 mJ/cm21 to 8 pulses• KrF 𝜆𝜆=248 nm, 25 ns, 300-700 mJ/cm21 to 8 pulses

Sb

Ge substrate

Ge

mel

tdep

th


( F. Sgarbossa et al., Appl. Surf. Sci. 496 (2019) )

Chemical profile evolution

16/9/2019 [email protected] – 4th PSeGe Workshop 7

• Sb incorporation at >10% concentration

• No surface segregation

• No Sb loss

• Diffusion confined in molten layer

0 2 4 6 8

1

10

ML

8nm

4nm

2nm

Sb d

ose

(101

5 /cm

2 )

PLM pulses

1nm

(RBS)

1019

1020

1021

1022

0 100 200 3001018

1019

1020

1021

1022

Nd-YAG 0.4 J/cm2

ML 2 nm 8 nm 1 pls 8 pls

KrF

Sb C

once

ntra

tion

(cm

-3)

Depth (nm)

ML 2 nm(0.5 J/cm2) (0.6 J/cm2)

1 pls 8 pls

Dopant activation

8

10191020

1021

1022ML 1 pulse

Sb c

once

ntra

tion

(cm

-3) SIMS = Active

1 nm 1 pls

SIMS Active

2 nm 1 pls 4 nm 1 pls 8 nm 1pls

0 100 200

10191020

1021ML 8 pls

100 200

1 nm 8 pls

100 200

2 nm 8 pls

Depth (nm)100 200

4 nm 8 pls

100 200

8 nm 8 pls

( )22

)()(

)()(

∫∫⋅

=dxxxne

dxxxnRHs

µ

µ

(R. Baron, G. Shifrin, O. Marsh and J. W. Mayer, and J. Menéndez, J. Appl. Phys. 40, 3702 (1969))

• Van der Pauw – Hall measurements• Maximum active concentration extracted

from measured RHs assuming SIMS profilesfully active below Nmax

• Hall scattering factor rH=1


Dopant activation


0 50 100 150 200

1019

1020

1021

Con

cent

ratio

n (c

m-3)

Depth (nm)

Sb (SIMS) Electrons (VdP-Hall) Electrons (diff. VdP-Hall)

• Alternating VdP-Hall measurements with chemical etching carrier depth profile

• Differential Van der Pauw – Hall measurements confirm active profile.

Dopant activation

10

1 10

1

2

3

4

5

VdP-Hall KrF VdP-Hall Nd:YAG FTIR Nd:YAG

Max

. ele

ctro

n co

ncen

tratio

n (1

020 /c

m3 )

Max. Sb concentration (1020/cm3)

100% activation

3x1020cm-3

• Active Sb saturates at 3x1020cm-3


FTIR

11

1000 2000 3000 4000 50000.0

0.2

0.4

0.6

0.8

1.0 4 nm Sb + PLM 4 pls Drude fit

Ref

lect

ance

Wavenumber (cm-1)

n=2,6·1020 cm-3Plasma wavelength λP ≤ 3 µm

• Active Sb saturates at 3x1020cm-3• Plasma wavelength below 3 µm


1 10

1

2

3

4

5


Max

. ele

ctro

n co

ncen

tratio

n (1

020 /c

m3 )


100% activation

3x1020cm-3

Resistivity and Mobility

12

P, As

Sb

P, As

Sb

• Active Sb saturates at 3x1020cm-3• Plasma wavelength below 3 µm• Ultralow resistivity• High mobility


1 10

1

2

3

4

5


Max

. ele

ctro

n co

ncen

tratio

n (1

020 /c

m3 )


100% activation

3x1020cm-3

10-4

10-3

Res

istiv

ity (Ω

cm

)

Our data (Nd:YAG) Our data (KrF) Cuttriss et al. 1963 Xu et al. 2016 Sb fit, (Xu 2016) P and As (Cuttris 1963)

1020 5x1020

100

200

300

400

Sb curve (calculated from Xu 2016)

P and As (Cuttris 1963)

Hal

l Mob

ility

(cm

2 /Vs)

Hall (γH=1) electron concentration (cm-3)

1 10

1

2

3

4

5


Max

. ele

ctro

n co

ncen

tratio

n (1

020 /c

m3 )


100% activation

3x1020cm-3

Substitutionality (c-RBS dip)

13

• C-RBS: Sb ∼100 % nearly substitutional with small displacements

(José Coutinho, et al., J. Mater. Sci. Mater. Electron. 2007)(A. Chroneos, J. Appl. Phys. 2010)

• After PLM inactive Sb is in the form of verysmall SbnV complexes.


HRXRD strain depth profiling

14

• Excellent cristallinity• Pseudomorphicity of doped layer• No sign of extended defects• Strain depth profiles extracted

32.6 32.8 33.0 33.2

Inte

nsity

(a.u

.)

θ (°)

Ge (004) Rocking Curve1020

1021

4nm Sb + PLM 8 pls

Sb c

once

ntra

tion

(cm

-3)

0 50 100 15010-4

10-3

10-2

mis

fit =

(aG

eSb

rel

-aG

e)/a G

e

Depth (nm)


-0,02 0,00 0,02

-0,04

-0,02

0,00

0,024nm Sb+Nd:YAG 8 pulses

∆Q⊥ (Å

-1)

∆Q// (Å-1)

Ge (444) Intensity

-0,02 0,00 0,02

∆Q// (Å-1)

1

1E+01

1E+02

1E+03

1E+04

1E+05

1E+062nm Sb+KrF@600mJ/cm2 1 pulse

HRXRD strain depth profiling

15

1020 1021

0,1

1 Our data Xu et al. 2016 Sb 100% active

(Xu, 2016)

mis

fit =

(aG

eSb

rel

-aG

e)/a G

e

Max. Sb concentration (cm-3)

• At low concentrations misfit aligns with literature data for 100% active Sb

• At high concentrations misfit continue to increase up to 0.7%


Conclusions

16

• The combination of Sb deposition and PLM provides an extremely efficient doping technique.

• Carrier concentration up to 3x1020cm-3 with record low resistivityand excellent mobility

• No bulk contamination as consequence of PLM


Conclusions

17

• The combination of Sb deposition and PLM provides an extremely efficient doping technique.

• Carrier concentration up to 3x1020cm-3 with record low resistivityand excellent mobility

• No bulk contamination as consequence of PLM• Pseudomorphic layers Ge:Sb layers with no extended defects• FTIR reports plasma wavelengths below 3 µm in the MIR range

useful for gas sensing applications

• Inactive Sb is nearly substitutional with small displacement, compatible with very small SbnV clusters.



Thanks for yourattention!

Chemical profile evolution

21

0 50 100 150 200

1019

1020

1021

1022

Sb C

once

ntra

tion

(cm

-3)

Depth (nm)

Monolayer

0 50 100 150 200

1 nm

Depth (nm)

0 50 100 150 200

8 nm

Depth (nm)

1 pulse 2 pulses 4 pulses 8 pulses

• Sb incorporation at >10% concentration

• No surface segregation

• No Sb loss


0 2 4 6 8

1

10

ML

8nm

4nm

2nm

Sb d

ose

(101

5 /cm

2 )

PLM pulses

1nm

(RBS)

23

0 1x1020 2x1020 3x1020 4x10200,000

0,001

0,002

0,003

0,004

0,005

0,006

0,007

Our Data 100% active

(Xu et al. 2016)

mis

fit (%

)

Max. active concentration (cm-3)


25

A. Chroneos, R. W. Grimes, B. P. Uberuaga, S. Brotzmann, and H. Bracht, Appl. Phys. Lett. 91, 192106 (2007).


HRXRD

26

0 1x1021 2x1021 3x1021 4x1021 5x10210.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Ge:Sb Fully active (Xu, 2016) Ge:Sb Size contribution (Xu, 2016)

mis

fit (%

)

Max. Sb concentration (cm-3)


n-type high doping of Ge by Sb deposition and pulsed laser melting Ge-based devicesGe hot topicsGe-based devicesDiapositiva numero 5Sb deposition + PLMChemical profile evolutionDopant activationDopant activationDopant activationFTIRResistivity and MobilitySubstitutionality (c-RBS dip)HRXRD strain depth profilingHRXRD strain depth profilingConclusionsConclusionsDiapositiva numero 18Diapositiva numero 19Diapositiva numero 20Chemical profile evolutionDiapositiva numero 23Diapositiva numero 24Diapositiva numero 25HRXRD

Sb doped Ge - Agenda (Indico) · 2019. 9. 25. · 1 n-type high doping of Ge by Sb deposition and...

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