sb doped ge - agenda (indico) · 2019. 9. 25. · 1 n-type high doping of ge by sb deposition and...
TRANSCRIPT
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n-type high doping of Ge by Sb deposition and pulsed laser melting
Carraro ChiaraPhD student Physics – Univ. Of Padova
4th Position Sensitive Germanium Detectors and Application Workshop (PSeGe)
16-19 Semptember 2019 – INFN LNL
16/9/2019
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Ge-based devices
2
Solar cells
Photodetectors
Plasmonic molecularsensors
Lasers
Nanolectronics
γ-Ray detectors
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Ge hot topics
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𝜔𝜔𝑝𝑝 ∝𝑛𝑛𝑚𝑚∗
n-type heavy doping
Strain engineering
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Ge-based devices
4
Solar cells
Photodetectors
Plasmonic molecularsensors
Lasers
Nanolectronics
γ-Ray detectors
[email protected] – 4th PSeGe Workshop16/9/2019
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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)
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Sb deposition + PLM
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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
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( F. Sgarbossa et al., Appl. Surf. Sci. 496 (2019) )
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Chemical profile evolution
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• 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
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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
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Dopant activation
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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.
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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
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FTIR
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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
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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
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Resistivity and Mobility
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P, As
Sb
P, As
Sb
• Active Sb saturates at 3x1020cm-3• Plasma wavelength below 3 µm• Ultralow resistivity• High mobility
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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
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)
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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
Substitutionality (c-RBS dip)
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• 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.
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HRXRD strain depth profiling
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• 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)
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-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
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HRXRD strain depth profiling
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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%
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Conclusions
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• 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
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Conclusions
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• 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.
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Thanks for yourattention!
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Chemical profile evolution
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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
[email protected] – 4th PSeGe Workshop17/9/2019
0 2 4 6 8
1
10
ML
8nm
4nm
2nm
Sb d
ose
(101
5 /cm
2 )
PLM pulses
1nm
(RBS)
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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)
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A. Chroneos, R. W. Grimes, B. P. Uberuaga, S. Brotzmann, and H. Bracht, Appl. Phys. Lett. 91, 192106 (2007).
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HRXRD
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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)
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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