The temperature dependence performance of ultraviolet radiation detectors T. V. Blank, Yu. A. Goldberg, O. V. Konstantinov Ioffe Physico-Technical Institute of Russian Academy of Science, St. Petersburg, Russia IWORID 2002 AMSTERDAM

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The temperature dependence performance of
ultraviolet radiation detectorsT. V. Blank, Yu.
A. Goldberg, O. V. KonstantinovIoffe
Physico-Technical Instituteof Russian Academy of
Science,St. Petersburg, RussiaIWORID 2002
AMSTERDAM
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Outline
Aim

• Determination of
• photoelectric conversion process mechanism in
  Schottky photodetectors
• temperature stability of UV detectors

• The temperature dependence of the quantum
  efficiency of GaP Schottky photodetectors.
• The fluctuation traps model.
• Comparison of the temperature dependencies of the
  quantum efficiency in Schottky and p-n
  photodetectors based on GaAs.
• The temperature dependence of the quantum
  efficiency of Si Schottky photodetectors.
• The temperature dependence of the quantum
  efficiency of 4H-SiC Schottky photodetectors.
• Conclusion.

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Experimental procedure

• where ? - quantum efficiency
• I - photocurrent
• ? - incident light power
• h? - photon energy
• q - electron charge

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The temperature dependence of the quantum
efficiency of GaP Schottky photodetectors
The quantum efficiency ? of GaP Schottky
photodetectors as a function of the temperature
for several photon energies.

• The spectrum of the quantum efficiency ? of GaP
  Schottky photodetectors at 300 K.

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Optical losses
Bulk losses
where R is reflection coefficient ? is
dielectric constant
Others losses
The effective optical length Ln of GaP as a
function of the photon energy, 300 K, W is the
width of the space-change region.

• surface recombination
• thermionic emission of thermalized and hot
  photoelectrons in the metal

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The fluctuation traps model

• ?(1-R)?(1-?hot)(1-?th?rm)
• 1-?th?rm?-??/kT
• ?1
• ?(1-R)(1-?hot)?-??/kT,
• where
• ? - quantum efficiency,
• R - reflection coefficient
• ? - internal quantum yield
• ?hot - loss factor of hot photocarriers
• ?th?rm - loss factor of thermalized photocarriers
• ?? - activation energy of the localized
  photocarriers
• k - Boltzmanns constant
• ? - temperature

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Schottky and p-n photodetectors based on GaAs
The spectrum of the quantum efficiency ? of
GaAs p-n photodetectors at 300 K.
The spectrum of the quantum efficiency ? of
GaAs Schottky photodetectors at 300 K.
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Comparison of the temperature dependencies of the
quantum efficiency in Schottky and p-n
photodetectors based on GaAs
The quantum efficiency ? of GaAs p-n
photodetectors as a function of the temperature
for several photon energies.
The quantum efficiency ? of GaAs Schottky
photodetectors as a function of the temperature
for several photon energies.
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The temperature dependence of the quantum
efficiency of p-n photodetectors based on Si
The spectrum of the quantum efficiency ? of Si
p-n photodetectors at 300 K
The quantum efficiency ? of Si p-n
photodetectors as a function of the temperature
for several photon energies.
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4H-SiC Schottky photodetectors

• The spectrum of the quantum efficiency ? of
  4H-SiC Schottky photodetectors at 300 K (line 1)
  and the spectrum of the relative effectiveness of
  different photon energies in bactericidal
  ultraviolet radiation (line 2).

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The temperature dependence of the quantum
efficiency of 4H-SiC Schottky photodetectors
At 300K W0.3 ?m Lh1.4 ?m L?thWoLh?1.7
?m??L?-1?hn4.5 eV where L? is effective
optical absorption length L?th is threshold
effective optical absorption length W is width of
the space-change region Lh is hole diffusion
length ? is absorption coefficient
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The photoelectric conversion mechanism in 4H-SiC
Schottky photodetectors
Band structure of 4H-SiC and scheme of different
optical transitions.
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Conclusion

• For Schottky photodetectors (based on GaAs, GaP,
  4H-SiC) the quantum efficiency increases with
  temperature for all photon energies.
• For p-n photodetectors based on GaAs and Si the
  quantum efficiency is temperature independent in
  the region of intrinsic absorption.
• Near-surface imperfections manifest themselves as
  the fluctuation traps and have an influence on
  the photoelectric conversion process in Schottky
  photodetectors.

Future

• The temperature dependence of the quantum
  efficiency of p-n and Schottky photodetectors
  based on GaN.
• The temperature dependence of the quantum
  efficiency of not deep p-n photodetectors (based
  on 4H-SiC).
• External electric field Influence on the quantum
  efficiency for UV photodetectors.