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![Page 1: Ultrafast carrier dynamics Optical Pump - THz Probe Ultrafast carrier dynamics in Br + -bombarded semiconductors investigated by Optical Pump - THz Probe.](https://reader035.fdocuments.us/reader035/viewer/2022062304/56649f1d5503460f94c33919/html5/thumbnails/1.jpg)
Ultrafast carrier dynamicsUltrafast carrier dynamicsin Br+-bombarded semiconductorsinvestigated by
Optical Pump - THz ProbeOptical Pump - THz Probespectroscopy
Jean-Christophe [email protected]
![Page 2: Ultrafast carrier dynamics Optical Pump - THz Probe Ultrafast carrier dynamics in Br + -bombarded semiconductors investigated by Optical Pump - THz Probe.](https://reader035.fdocuments.us/reader035/viewer/2022062304/56649f1d5503460f94c33919/html5/thumbnails/2.jpg)
April 2009 JPU 2009 2
Outline
• IntroductionIntroduction• Experimental SetupExperimental Setup• Samples preparationSamples preparation• ResultsResults
– InPInP– InGaAsInGaAs
• PespectivesPespectives
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April 2009 JPU 2009 3
Introduction & Motivations
• Generation of coherent terahertz pulses in ultrafast semiconductors (LT-AsGa and other materials)
• Specific methods aim to increase the concentration of traps:– Film growth and Doping– Implantation or Irradiation with heavy ions
• Ionic irradiation: efficient method of engineering the carrier lifetime. How are the carrier lifetime How are the carrier lifetime and dynamics affected?and dynamics affected?
• Present study: Transient Terahertz Spectroscopic Transient Terahertz Spectroscopic study of the effect of Brstudy of the effect of Br++ irradiation irradiation of InGaAs of InGaAs and InP on the carrier lifetime and mobilityand InP on the carrier lifetime and mobility
IntroductionSetupSamples ResultsPespectives
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April 2009 JPU 2009 4
Why using THz in SC science?
• THz Radiation is indeed a valuable tool for (true) optoelectronics studies
ElectronicsGunn Diodep-i-n DiodeHigh mobility transistor (HEMT)
OpticsNL OpticsUltrafast LasersQCL
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April 2009 JPU 2009 5
Why using THz in SC science?
• THz Radiation is indeed a valuable tool for (true) optoelectronics studies
ElectronicsGunn Diodep-i-n DiodeHigh mobility transistor (HEMT)
OpticsNL OpticsUltrafast LasersQCL
![Page 6: Ultrafast carrier dynamics Optical Pump - THz Probe Ultrafast carrier dynamics in Br + -bombarded semiconductors investigated by Optical Pump - THz Probe.](https://reader035.fdocuments.us/reader035/viewer/2022062304/56649f1d5503460f94c33919/html5/thumbnails/6.jpg)
April 2009 JPU 2009 6
Experimental Setup
Pump:=810 nm (fs, CPA)
Probe:Broadband (ps) THz
Collinear Pump-Probe
Geometry: Ultimate Temporal Resolution (limited only by thedetector
response)<ps
Low excitation experiment: few µJ/pulse – w0~2mmInitial carrier concentrations: 1016<n0<1018 cm-3
Setup in vacuum box to prevent water absorption
IntroductionSetupSamples ResultsPespectives
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April 2009 JPU 2009 7
Experimental Setup
Pump:=810 nm (fs, CPA)
Probe:Broadband (ps) THz
Collinear Pump-Probe
Geometry: Ultimate Temporal Resolution (limited only by thedetector
response)<ps
Low excitation experiment: few µJ/pulse – w0~2mmInitial carrier concentrations: 1016<n0<1018 cm-3
Setup in vacuum box to prevent water absorption
IntroductionSetupSamples ResultsPespectives
Optical Rectification(‘0’ frequency DFG)
(2)(,;~0)
ETHz(t)Iopt(t)
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April 2009 JPU 2009 8
Experimental Setup
Pump:=810 nm (fs, CPA)
Probe:Broadband (ps) THz
Collinear Pump-Probe
Geometry: Ultimate Temporal Resolution (limited only by thedetector
response)<ps
Low excitation experiment: few µJ/pulse – w0~2mmInitial carrier concentrations: 1016<n0<1018 cm-3
Setup in vacuum box to prevent water absorption
IntroductionSetupSamples ResultsPespectives
![Page 9: Ultrafast carrier dynamics Optical Pump - THz Probe Ultrafast carrier dynamics in Br + -bombarded semiconductors investigated by Optical Pump - THz Probe.](https://reader035.fdocuments.us/reader035/viewer/2022062304/56649f1d5503460f94c33919/html5/thumbnails/9.jpg)
April 2009 JPU 2009 9
Experimental Setup
Pump:=810 nm (fs, CPA)
Probe:Broadband (ps) THz
Collinear Pump-Probe
Geometry: Ultimate Temporal Resolution (limited only by thedetector
response)<ps
Low excitation experiment: few µJ/pulse – w0~2mmInitial carrier concentrations: 1016<n0<1018 cm-3
Setup in vacuum box to prevent water absorption
IntroductionSetupSamples ResultsPespectives
ETHz(t): Transient modifications of ETHz(t) (waveform) are recorded in time for different pump-probe delays
Equilibrium Photoexcitation RelaxationScattering
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April 2009 JPU 2009 10
Experimental Setup
Pump:=810 nm (fs, CPA)
Probe:Broadband (ps) THz
Collinear Pump-Probe
Geometry: Ultimate Temporal Resolution (limited only by thedetector
response)<ps
Low excitation experiment: few µJ/pulse – w0~2mmInitial carrier concentrations: 1016<n0<1018 cm-3
Setup in vacuum box to prevent water absorption
IntroductionSetupSamples ResultsPespectives
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April 2009 JPU 2009 11
Samples Preparation
0
1
2
3
4
5
6
7
8
Im
plan
tati
on d
ensi
ty (
103 c
m–3
/cm
–2)
Depth (µm)
In0.47Ga0.53As InP
0 3 6 0
1
2
3
4
5
6
7
Im
plan
tati
on d
ensi
ty (
103 c
m–3
/cm
–2)
Depth (µm)
InP
0 3 6
Depth (µm) 0 3 6
InP
0.0
0.2
0.4
0.6
0.8 D
ensi
ty o
f in
trin
sic
radi
atio
n in
duce
d de
fect
s (1
08 cm
–3/c
m–2
) 0.9
0.7
0.5
0.3
0.1
Depth (µm) 0 3 6
In0.47Ga0.53As InP
0.0
0.2
0.4
0.6
0.8
1.0
Den
sity
of
intr
insi
c ra
diat
ion
indu
ced
defe
cts
(108 c
m–3
/cm
–2)
11 Mev Br+ ions: deep implantation
IntroductionSetupSamples ResultsPespectives
[Br] [Br]
[def] [def]
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April 2009 JPU 2009 12
Samples Preparation
0
1
2
3
4
5
6
7
8
Im
plan
tati
on d
ensi
ty (
103 c
m–3
/cm
–2)
Depth (µm)
In0.47Ga0.53As InP
0 3 6 0
1
2
3
4
5
6
7
Im
plan
tati
on d
ensi
ty (
103 c
m–3
/cm
–2)
Depth (µm)
InP
0 3 6
Depth (µm) 0 3 6
InP
0.0
0.2
0.4
0.6
0.8 D
ensi
ty o
f in
trin
sic
radi
atio
n in
duce
d de
fect
s (1
08 cm
–3/c
m–2
) 0.9
0.7
0.5
0.3
0.1
Depth (µm) 0 3 6
In0.47Ga0.53As InP
0.0
0.2
0.4
0.6
0.8
1.0
Den
sity
of
intr
insi
c ra
diat
ion
indu
ced
defe
cts
(108 c
m–3
/cm
–2)
11 Mev Br+ ions: deep implantation
Bulk InPBulk InP
IntroductionSetupSamples ResultsPespectives
[Br] [Br]
[def] [def]
Stopping Range of Ions in the Matter
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April 2009 JPU 2009 13
Samples Preparation
0
1
2
3
4
5
6
7
8
Im
plan
tati
on d
ensi
ty (
103 c
m–3
/cm
–2)
Depth (µm)
In0.47Ga0.53As InP
0 3 6 0
1
2
3
4
5
6
7
Im
plan
tati
on d
ensi
ty (
103 c
m–3
/cm
–2)
Depth (µm)
InP
0 3 6
Depth (µm) 0 3 6
InP
0.0
0.2
0.4
0.6
0.8 D
ensi
ty o
f in
trin
sic
radi
atio
n in
duce
d de
fect
s (1
08 cm
–3/c
m–2
) 0.9
0.7
0.5
0.3
0.1
Depth (µm) 0 3 6
In0.47Ga0.53As InP
0.0
0.2
0.4
0.6
0.8
1.0
Den
sity
of
intr
insi
c ra
diat
ion
indu
ced
defe
cts
(108 c
m–3
/cm
–2)
11 Mev Br+ ions: deep implantation
Etched InPEtched InP
IntroductionSetupSamples ResultsPespectives
[Br] [Br]
[def] [def]
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April 2009 JPU 2009 14
Samples Preparation
0
1
2
3
4
5
6
7
8
Im
plan
tati
on d
ensi
ty (
103 c
m–3
/cm
–2)
Depth (µm)
In0.47Ga0.53As InP
0 3 6 0
1
2
3
4
5
6
7
Im
plan
tati
on d
ensi
ty (
103 c
m–3
/cm
–2)
Depth (µm)
InP
0 3 6
Depth (µm) 0 3 6
InP
0.0
0.2
0.4
0.6
0.8 D
ensi
ty o
f in
trin
sic
radi
atio
n in
duce
d de
fect
s (1
08 cm
–3/c
m–2
) 0.9
0.7
0.5
0.3
0.1
Depth (µm) 0 3 6
In0.47Ga0.53As InP
0.0
0.2
0.4
0.6
0.8
1.0
Den
sity
of
intr
insi
c ra
diat
ion
indu
ced
defe
cts
(108 c
m–3
/cm
–2)
11 Mev Br+ ions: deep implantation
InGaAsInGaAs
IntroductionSetupSamples ResultsPespectives
[Br] [Br]
[def] [def]
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April 2009 JPU 2009 15
InP: Results
• Slow SamplesTransient modifications of the peak in the THz waveform vs. Pump-Probe delay p (1D Scan).
Spectrally averaged (unresolved) information about the carrier lifetime c
Time Resolved detection of the Terahertz waveform: Complex spectrum (Real & Imag. part) of the surface conductivity
InPInP
IntroductionSetupSamples ResultsPespectives
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April 2009 JPU 2009 16
InP: Results
• Slow SamplesSurface conductivity
InPInP
IntroductionSetupSamples ResultsPespectives
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April 2009 JPU 2009 17
InP: Results
• Fast Samples
FT along time FT along pump-probe delay
Time dependent spectrum
2D spectrum
Dynamics in 1011 and 1012 cm-2 samples is very fast (no quasi-dc analysis) 2D Fourier transformation provides a proper deconvolution
H. Němec, et al., J. Chem. Phys. 122, 104503 (2005)
TimeDependentWaveforms
InPInP
IntroductionSetupSamples ResultsPespectives
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April 2009 JPU 2009 18
InP: Results
• Fast Samples
20 0
p 1 1 1eff p
1 1( , )
2 2s c c
n ef f
m if if
InPInP
Experimental 2D spectrum of the surface conductivity
Drude model Fit
Residuum exhibits no features
GOOD AGREEMENT WITH A DRUDE MODEL
IntroductionSetupSamples ResultsPespectives
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April 2009 JPU 2009 19
InP: Results
• Power Dependence
tht
t
h
hhh
h
hett
t
h
h
t
t
e
et
tet
t
e
eee
e
ngN
nn
z
nD
t
n
ggnN
nn
N
nn
t
n
ngN
nn
z
nD
t
n
2
2
2
2
1
1
Shockley-Read modelShockley-Read model
1
1exp
1exp
ee t
e t B
ghh t
h t B
N Eg
N k T
E ENg
N k T
0 10 20 30Pump-probe delay (ps)
5
4
3
2
1
0
10
3
S (
-1)
Sample E10
n0 = 0.9×1017 cm-3
n0 = 2.2×1017 cm-3
n0 = 4.9×1017 cm-3
Large pump spot:No transverse diffusionNo transverse diffusion
InPInP
IntroductionSetupSamples ResultsPespectives
Phys. Rev. B, 78, 235206 (2008)
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April 2009 JPU 2009 20
InP Results: Summary
Sample nIRRAD (cm–3) nBr (cm–3) n0 (cm–3) s (fs) 0 (cm2V–1s–1) decay (ps)
B9 2×1016 0 1.6×1017 140 3000 490
E9 9×1016 5×1012 1.1×1017 120 2600 70
B10 2×1017 0 1.6×1017 120 2700 100
E10 9×1017 5×1013 0.9×1017 100 2100 5.5
B11 2×1018 0 1.6×1017 70 1600 2.6
E11 9×1018 5×1014 2.2×1017 90 2100 1.2
B12 2×1019 0 1.6×1017 40 900 0.29
Influence of Br+ ion concentration on Bulk and Etched sample parameters
Carriers lifetime:-Due to density of induced defects-Not significantly influenced by Br implantation
Trapping time decreases Trapping time decreases by 3 orders of by 3 orders of magnitude (Log)magnitude (Log)
Mobility decreases only Mobility decreases only by a factor 3 (Linear)by a factor 3 (Linear)
InPInP
IntroductionSetupSamples ResultsPespectives
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April 2009 JPU 2009 21
InGaAs: Results
• Slow Samples
Dose(cm–2)
s
(fs)c
(ps) R/R(ps)
0,THz 0,Hall
(cm2V–1s-1)
109 0.25 297 ± 5 >500(*) 2600 10800
1010 0.22 43± 5 10 2100 --
1011 0.175 3.4± 2 <0.4 1900 4300
0 10 20 30 40 50time ps
3
2
1
0
Det
ecte
d si
gnal
(a.
u.)
C scan Sample B 5mW
C scan sample A 5mW
C scan Sample C 5mw
InGaAsInGaAs
(*)undoped
IntroductionSetupSamples ResultsPespectives
Single Component
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April 2009 JPU 2009 22
In1-xGaxAs: Results
• Fast Samples
InGaAsInGaAs
(x=0.47)
-4 -3 -2 -1 0 1 2 3 4
f p (THz)
-2-1.5
-1-0.5
00.5
11.5
2
f (T
Hz)
0
3000
6000
9000
theo(fp,f)1,2,3
ii
Conductivity: Sum of several contributions (3 paths)
IntroductionSetupSamples ResultsPespectives
Excitation
Ground state
State 2 (L-valley)State 1 (-valley)
c,1
23
c,2
Drude response (s,2)State 3 (-valley)
c,3
13
12
21
Fit of the 2D spectrum
gives access to the ’s
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April 2009 JPU 2009 23
In1-xGaxAs DynamicsInGaAsInGaAs
(x=0.47)
mL = 0.29 me
mX = 0.68 me
IntroductionSetupSamples ResultsPespectives
m = 0.041 me
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April 2009 JPU 2009 24
In1-xGaxAs DynamicsInGaAsInGaAs
(x=0.47)
mL = 0.29 me
mX = 0.68 me
IntroductionSetupSamples ResultsPespectives
m = 0.041 me
![Page 25: Ultrafast carrier dynamics Optical Pump - THz Probe Ultrafast carrier dynamics in Br + -bombarded semiconductors investigated by Optical Pump - THz Probe.](https://reader035.fdocuments.us/reader035/viewer/2022062304/56649f1d5503460f94c33919/html5/thumbnails/25.jpg)
April 2009 JPU 2009 25
In1-xGaxAs DynamicsInGaAsInGaAs
(x=0.47)
mL = 0.29 me
mX = 0.68 me
IntroductionSetupSamples ResultsPespectives
m = 0.041 me
![Page 26: Ultrafast carrier dynamics Optical Pump - THz Probe Ultrafast carrier dynamics in Br + -bombarded semiconductors investigated by Optical Pump - THz Probe.](https://reader035.fdocuments.us/reader035/viewer/2022062304/56649f1d5503460f94c33919/html5/thumbnails/26.jpg)
April 2009 JPU 2009 26
In1-xGaxAs DynamicsInGaAsInGaAs
(x=0.47)
mL = 0.29 me
mX = 0.68 me
IntroductionSetupSamples ResultsPespectives
m = 0.041 me
… and further slow relaxation …
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April 2009 JPU 2009 27
In1-xGaxAs DynamicsInGaAsInGaAs
(x=0.47)
mL = 0.29 me
mX = 0.68 me
IntroductionSetupSamples ResultsPespectives
m = 0.041 me
… Somehow complicated …
Improvement of the theoretical model byS.E.Ralph et al, Phys. Rev. B 54, 5568
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April 2009 JPU 2009 28
Conclusion
Time-resolved THz spectroscopy in Br+-bombarded : InP & In0.53Ga0.47AsCharacterization of : Lifetime & Mobility
For density of induced defects (not [Br+]) both Lifetime and Mobility
InP (Most irradiated):• carrier lifetime 3 orders of magnitude• mobility of carriers only reduced by factor 3only reduced by factor 3 (vs. as-grown sample)• carrier trappingtrapping and carrier diffusiondiffusion
In1-xGaxAs: • As found in InP, both electron mobility and lifetime are reduced• Very high photoexcited mobilityVery high photoexcited mobility 3600 cm2V–1s–1 + 460 fs lifetime • Changing x and [Br+] : large tunabilty of optical and electronic material
parameters Improvement of ultrafast optoelectronic devices based on this material. High potentialHigh potential for THz optoelectronicTHz optoelectronic at 1.5 µm1.5 µm
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April 2009 JPU 2009 29
Perspectives
• Wavelength dependence:– Penetration depth / Initial profile– Electronic State
• Temperature dependence
• Clusters of defects
• Automated Measurement:– Single shot waveform + pump-probe– Single shot 2D
IntroductionSetupSamples ResultsPespectives
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April 2009 JPU 2009 30
Subpicosecond Non Contact Ohmmeter
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April 2009 JPU 2009 31
Acknowledgments
• CPMOH
• Sample preparation, dc and optical characterisation
• Experiment hosted in Prag
• Support for international exchange
E.N’Guema, L.Canioni, P.Mounaix
H.Němec, L.Fekete, F.Kadlec, P.Kužel
M.Martin, J.Mangeney
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Thank you for Thank you for your attentionyour attention