Vancouver 081 Free carrier induced substrate heating of the epitaxially grown GaMnAs Institute of...
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![Page 1: Vancouver 081 Free carrier induced substrate heating of the epitaxially grown GaMnAs Institute of Physics AS CR, Prague Vit Novak, Kamil Olejnik, Miroslav.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649de55503460f94adc9dc/html5/thumbnails/1.jpg)
Vancouver 08 1
Free carrier induced substrate Free carrier induced substrate heating of the epitaxially grown heating of the epitaxially grown GaMnAsGaMnAs
Institute of Physics AS CR, Prague
Vit Novak, Kamil Olejnik, Miroslav Cukr
![Page 2: Vancouver 081 Free carrier induced substrate heating of the epitaxially grown GaMnAs Institute of Physics AS CR, Prague Vit Novak, Kamil Olejnik, Miroslav.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649de55503460f94adc9dc/html5/thumbnails/2.jpg)
Vancouver 08 2
GaMnAsGaMnAs
• Problem: limited Mn solubility
growth at T=220°C growth at T=230°C
7%Mn, 50 nm 7%Mn, 50 nm
![Page 3: Vancouver 081 Free carrier induced substrate heating of the epitaxially grown GaMnAs Institute of Physics AS CR, Prague Vit Novak, Kamil Olejnik, Miroslav.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649de55503460f94adc9dc/html5/thumbnails/3.jpg)
Vancouver 08 3
Measuring the (low) temperatureMeasuring the (low) temperature
• thermocouple x poor coupling
• optical pyrometry x weak radiation
x substrate transparent
• Band-gap spectroscopy
Shanabrook et al. (1992), Johnson et al. (1993),
Thompson et al. (1997)
commercially by kSA (BandiT)
![Page 4: Vancouver 081 Free carrier induced substrate heating of the epitaxially grown GaMnAs Institute of Physics AS CR, Prague Vit Novak, Kamil Olejnik, Miroslav.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649de55503460f94adc9dc/html5/thumbnails/4.jpg)
Vancouver 08 4
Band-gap spectroscopyBand-gap spectroscopy
spectrometer
substrate heater
GaAs
160°C sufficient!
>~
![Page 5: Vancouver 081 Free carrier induced substrate heating of the epitaxially grown GaMnAs Institute of Physics AS CR, Prague Vit Novak, Kamil Olejnik, Miroslav.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649de55503460f94adc9dc/html5/thumbnails/5.jpg)
Vancouver 08 5
GrowthGrowth
• minimum change in Ts measured by Tc
constant heater power
![Page 6: Vancouver 081 Free carrier induced substrate heating of the epitaxially grown GaMnAs Institute of Physics AS CR, Prague Vit Novak, Kamil Olejnik, Miroslav.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649de55503460f94adc9dc/html5/thumbnails/6.jpg)
Vancouver 08 6
GrowthGrowth
• minimum change in Ts measured by Tc
• large change in Ts measured by BES !
constant heater power
![Page 7: Vancouver 081 Free carrier induced substrate heating of the epitaxially grown GaMnAs Institute of Physics AS CR, Prague Vit Novak, Kamil Olejnik, Miroslav.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649de55503460f94adc9dc/html5/thumbnails/7.jpg)
Vancouver 08 7
Absorption spectrumAbsorption spectrum
substrate
+ GaMnAs
band-gap region
![Page 8: Vancouver 081 Free carrier induced substrate heating of the epitaxially grown GaMnAs Institute of Physics AS CR, Prague Vit Novak, Kamil Olejnik, Miroslav.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649de55503460f94adc9dc/html5/thumbnails/8.jpg)
Vancouver 08 8
Absorption spectrumAbsorption spectrum
really change of Ts !
substrate
+ 40°C
+ GaMnAs
band-gap region
![Page 9: Vancouver 081 Free carrier induced substrate heating of the epitaxially grown GaMnAs Institute of Physics AS CR, Prague Vit Novak, Kamil Olejnik, Miroslav.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649de55503460f94adc9dc/html5/thumbnails/9.jpg)
Vancouver 08 9
Absorption spectrumAbsorption spectrum
really change of Ts !
substrate
+ 40°C
+ GaMnAs
band-gap region NIR
phononsfree carriers
substrate
+ GaMnAs
![Page 10: Vancouver 081 Free carrier induced substrate heating of the epitaxially grown GaMnAs Institute of Physics AS CR, Prague Vit Novak, Kamil Olejnik, Miroslav.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649de55503460f94adc9dc/html5/thumbnails/10.jpg)
Vancouver 08 10
Model I.Model I.
naively:
solution:
But ! • obscured parameters
• inconsistencies with experiment
![Page 11: Vancouver 081 Free carrier induced substrate heating of the epitaxially grown GaMnAs Institute of Physics AS CR, Prague Vit Novak, Kamil Olejnik, Miroslav.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649de55503460f94adc9dc/html5/thumbnails/11.jpg)
Vancouver 08 11
Radiation heat exchangeRadiation heat exchange
1 2
Qin-2
Qout-2Qout-1
![Page 12: Vancouver 081 Free carrier induced substrate heating of the epitaxially grown GaMnAs Institute of Physics AS CR, Prague Vit Novak, Kamil Olejnik, Miroslav.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649de55503460f94adc9dc/html5/thumbnails/12.jpg)
Vancouver 08 12
Radiation heat exchangeRadiation heat exchange
1 2
Qin-2
Qout-2Qout-1
![Page 13: Vancouver 081 Free carrier induced substrate heating of the epitaxially grown GaMnAs Institute of Physics AS CR, Prague Vit Novak, Kamil Olejnik, Miroslav.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649de55503460f94adc9dc/html5/thumbnails/13.jpg)
Vancouver 08 13
Radiation heat exchangeRadiation heat exchange
phononsinterband
• substrate/epilayer absorptance s()
abso
rpta
nce
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Vancouver 08 14
Radiation heat exchangeRadiation heat exchange
phononsinterband
free holes
abso
rpta
nce
• substrate/epilayer absorptance s()
![Page 15: Vancouver 081 Free carrier induced substrate heating of the epitaxially grown GaMnAs Institute of Physics AS CR, Prague Vit Novak, Kamil Olejnik, Miroslav.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649de55503460f94adc9dc/html5/thumbnails/15.jpg)
Vancouver 08 15
Radiation heat exchangeRadiation heat exchange
phononsinterband
free holesabso
rpta
nce
• substrate/epilayer absorptance s()
![Page 16: Vancouver 081 Free carrier induced substrate heating of the epitaxially grown GaMnAs Institute of Physics AS CR, Prague Vit Novak, Kamil Olejnik, Miroslav.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649de55503460f94adc9dc/html5/thumbnails/16.jpg)
Vancouver 08 16
Radiation heat exchangeRadiation heat exchange
phononsinterband
free holes
abso
rpta
nce
• substrate/epilayer absorptance s()
![Page 17: Vancouver 081 Free carrier induced substrate heating of the epitaxially grown GaMnAs Institute of Physics AS CR, Prague Vit Novak, Kamil Olejnik, Miroslav.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649de55503460f94adc9dc/html5/thumbnails/17.jpg)
Vancouver 08 17
Radiation heat exchangeRadiation heat exchange
phononsinterband
• radiation sources
free holes
~250°C
abso
rpta
nce,
rad
ianc
e
![Page 18: Vancouver 081 Free carrier induced substrate heating of the epitaxially grown GaMnAs Institute of Physics AS CR, Prague Vit Novak, Kamil Olejnik, Miroslav.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649de55503460f94adc9dc/html5/thumbnails/18.jpg)
Vancouver 08 18
Radiation heat exchangeRadiation heat exchange
phononsinterband
~900°C
• radiation sources
free holes
abso
rpta
nce
abso
rpta
nce,
rad
ianc
e
~250°C
![Page 19: Vancouver 081 Free carrier induced substrate heating of the epitaxially grown GaMnAs Institute of Physics AS CR, Prague Vit Novak, Kamil Olejnik, Miroslav.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649de55503460f94adc9dc/html5/thumbnails/19.jpg)
Vancouver 08 19
Radiation heat exchangeRadiation heat exchange
phononsinterband
• radiation sources
free holes
backgroundabso
rpta
nce,
rad
ianc
e
~250°C
~900°C
![Page 20: Vancouver 081 Free carrier induced substrate heating of the epitaxially grown GaMnAs Institute of Physics AS CR, Prague Vit Novak, Kamil Olejnik, Miroslav.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649de55503460f94adc9dc/html5/thumbnails/20.jpg)
Vancouver 08 20
Radiation heat exchangeRadiation heat exchange
phononsinterband
• substrate radiation
free holes
background
substrate
abso
rpta
nce,
rad
ianc
e
~250°C
~900°C
![Page 21: Vancouver 081 Free carrier induced substrate heating of the epitaxially grown GaMnAs Institute of Physics AS CR, Prague Vit Novak, Kamil Olejnik, Miroslav.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649de55503460f94adc9dc/html5/thumbnails/21.jpg)
Vancouver 08 21
Model II.Model II.
better:
heater ( 200°C )
cells ( ~ 900°C )
background ( > 77K, < 200°C )
i : >~
s(, t) :t
f
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Vancouver 08 22
ResultsResults
before growth: long after growth:
![Page 23: Vancouver 081 Free carrier induced substrate heating of the epitaxially grown GaMnAs Institute of Physics AS CR, Prague Vit Novak, Kamil Olejnik, Miroslav.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649de55503460f94adc9dc/html5/thumbnails/23.jpg)
Vancouver 08 23
ResultsResults
before growth: long after growth:
time evolution: Th = 320°C
Tc = 950°C
Tb = 40°C
![Page 24: Vancouver 081 Free carrier induced substrate heating of the epitaxially grown GaMnAs Institute of Physics AS CR, Prague Vit Novak, Kamil Olejnik, Miroslav.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649de55503460f94adc9dc/html5/thumbnails/24.jpg)
Vancouver 08 24
Implications for Implications for T T reductionreduction• TBES-locked substrate heater power
(problem: heat capacity of heater)
![Page 25: Vancouver 081 Free carrier induced substrate heating of the epitaxially grown GaMnAs Institute of Physics AS CR, Prague Vit Novak, Kamil Olejnik, Miroslav.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649de55503460f94adc9dc/html5/thumbnails/25.jpg)
Vancouver 08 25
Implications for Implications for T T reductionreduction• TBES-locked substrate heater power
(problem: heat capacity of heater)
• sample holder (or sample!) with initially strong IR absorption
![Page 26: Vancouver 081 Free carrier induced substrate heating of the epitaxially grown GaMnAs Institute of Physics AS CR, Prague Vit Novak, Kamil Olejnik, Miroslav.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649de55503460f94adc9dc/html5/thumbnails/26.jpg)
Vancouver 08 26
Implications for Implications for T T reductionreduction• TBES-locked substrate heater power
(problem: heat capacity of heater)
• sample holder (or sample!) with initially strong IR absorption
![Page 27: Vancouver 081 Free carrier induced substrate heating of the epitaxially grown GaMnAs Institute of Physics AS CR, Prague Vit Novak, Kamil Olejnik, Miroslav.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649de55503460f94adc9dc/html5/thumbnails/27.jpg)
Vancouver 08 27
Implications for Implications for T T reductionreduction• TBES-locked substrate heater power
(problem: heat capacity of heater)
• sample holder (or sample!) with initially strong IR absorption
![Page 28: Vancouver 081 Free carrier induced substrate heating of the epitaxially grown GaMnAs Institute of Physics AS CR, Prague Vit Novak, Kamil Olejnik, Miroslav.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649de55503460f94adc9dc/html5/thumbnails/28.jpg)
Vancouver 08 28
Implications for Implications for T T reductionreduction• TBES-locked substrate heater power
(problem: heat capacity of heater)
on Mo-block
w/ sublayer
• sample holder (or sample!) with initially strong IR absorption
![Page 29: Vancouver 081 Free carrier induced substrate heating of the epitaxially grown GaMnAs Institute of Physics AS CR, Prague Vit Novak, Kamil Olejnik, Miroslav.](https://reader030.fdocuments.us/reader030/viewer/2022032801/56649de55503460f94adc9dc/html5/thumbnails/29.jpg)
Vancouver 08 29
Bonus: record Curie temperatureBonus: record Curie temperature
185K
also: Nottingham group
Thank you !Thank you !