IR detectors state of the art

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• IR detectors state of the art
• Elena Plis
• Mentor Dr. J.-B. Rodriguez

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Two classes of IR detectors

• The time response of photon detectors is
• faster than that of the corresponding thermal
  detectors

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Photon detectors
Photon Detectors

• Conductivity is improved by the presence of the
  photon-generated carriers

• Generate an electromotive force when photons are
  detected

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Performance of ideal photon detectors
Responsivity of ideal photon detector with
different quantum efficiencies.
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Performance of ideal photon and thermal detectors
BLIP limited D versus peak cutoff wavelength for
ideal photovoltaic (PV), photoconductor (PC) and
thermal detectors.
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Spectral detectivity of various detectors
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Microbolometers

• Near room temperature operation
• Lower cost and increased reliability
• Problems
• - no multispectral detection
• - less sensitive and produce poorer
  quality
• images than their cooled
  counterparts

Thermal detector mounted via lags to heat sink
Magnified view of microbolometers array
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HgCdTe Detectors

• High quantum efficiency (60-75)
• Dual-band detectors being made
• Tunability of band-gap energy
• Problems
• - a sensitive dependence of the energy
  gap on the alloy composition ratio, requiring
  a precise control over the growth temperature
  (?T1-5?C) during the growth
• - large non-uniformity over large
  area
• - large tunneling currents due to low
  electron effective mass
• - low operational temperature.

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InSb Detectors

• High quantum efficiency (60-75)
• High uniformity
• Large formats of FPAs available
• - 2K X 2K arrays
• Problems
• - spectral response shifts to longer
  wavelength with increasing temperature
• (thermally generated noise
  increases with temperature)
• - InSb infrared FPAs have been found
  to drift in their nonuniformity
• characteristics over time and
  from cool down to cool down (thermoelectric
  coolers
• and additional electronics in the
  camera is required)
• - low operational temperature.

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QWIP Detectors

• Use of standard manufacturing techniques based
  on mature GaAs growth and
• processing technologies
• High spatial uniformity
• High yield and low cost
• Good thermal stability
• Problems
• - cannot couple photons at normal
  incidence (grating on the surface is
• required)
• - typically have a narrow response
  range in the infrared
• - limited by tunneling currents
• - low quantum efficiency ( 10).

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QDIP Detectors

• QDIPs are not sensitive to the direction of
  incident light
• Theoretically predicted better performance for
  QDIPs if compare with QWIPs
• - QDIPs have a broader IR
  response range
• - QDIPs have lower dark current
• - QDIPs have higher responsivity.
• Problems
• - QDIPs potential was not yet
  realized completely

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SLs Detectors

• Problems
• - .SLs potential was not yet
  realized completely

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Comparison of competitive technologies
Third generation IR systems have to provide the
following capabilities

• High sensitivity and, consequently, high thermal
  contrast of the collected image.
• Large formats of detectors with high uniformity
  across the detector array
• Multispectral detection (MWIR/LWIR) and lower
  cross-talk.
• Operation at higher FPA temperatures (gt200K) to
  reduce cryogenics constraints
• and to improve reliability
• The decrease in global system cost
• Lower pixel size

Theoretically predicted
Practically implemented
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Comparison of competitive technologies MWIR (3-5
?m)
1.1 x 109

• Given parameters describe performance of FPAs
• All parameters are given at maximal operational
  temperature
• if not stated otherwise

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MCT Detectors for RT operation

• HgCdTe diodes for room temperature operation
• - (1-2.6)?m wavelength region
• - responsivity _at_ ?peak 2.6 ?m
  is equal to 1A/W
• - D gt 2.0e10 J
• - Manufacturer Fermionics
  corporation, USA

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Some major manufacturers of IR FPAs