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Materials for High-Temperature Semiconductor Devices (1995) / Chapter Skim
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Device Physics: Behavior at Elevated Temperatures
Pages 31-38

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From page 31...
... Figure 3.2 shows the calculated electron mobility as a function temperature for e-type GaN, doped 10~7 cm~3. Intrinsic Carrier Concentrations: Dependence on Bandgap Energy and Temperature Thermal energy, kT, can be sufficient to promote electrons from the valence band to the conduction band, giving rise to a thermally generated current, which is not
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From page 32...
... is to increase ni, hence leakage current. This is a critical concern for technologies that depend on an insulating or semi-insulating substrate, which is the case for GaAs metal semiconductor field effect transistors (MESFETs)
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From page 33...
... Breakdown voltages, mobilities, and saturation velocities will be degraded in all cases, but should fall off with temperature less precipitously for the wide bandgap materials than for silicon or GaAs. For JFM, the high breakdown field dominates, making all of the wide bandgap materials attractive compared to silicon, germanium, and GaAs.
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From page 34...
... The figures of merit suggest that devices whose limitations are principally due to their electronic limitations, such as saturated velocity or breakdown electric field, can achieve higher power density in the wide bandgap materials. Field effect transistors are among this class of devices.
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From page 35...
... This in turn can bring about an increased collector-emitter saturation voltage, V`e
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From page 36...
... For silicon technology, transistor operation has been demonstrated up to 450 °C (Migitaka and Kurachi, 1994~; since leakage currents are already large at this temperature, it is unlikely that silicon devices will be operated at significantly higher temperatures. Since analog-device operation is more strongly affected by the changes in leakage current, gain, and threshold voltages that occur with temperature, it is estimated by the committee that high-temperature operation of these devices will hold good to only 350 °C.
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From page 37...
... 300 400 500 600 700 800 Amp Current operating temperature - FIGURE 3-7 Operating temperatures for different devices per material. by the changes in leakage currents, gain, and threshold voltages caused by high temperature.
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From page 38...
... To uncover the true limitations or capabilities will require further experimentation. The intention is to more clearly focus on desired operating temperatures and the concomitant most promising device technologies in those temperature regimes.
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Key Terms

  • leakage current
  • wide bandgap
  • leakage currents
  • bandgap materials
  • intrinsic carrier

  • reverse leakage
  • power devices
  • carrier density
  • digital logic
  • effect transistors

  • device performance
  • field effect
  • electric field
  • threshold voltage
  • calculated electron

  • strongly affected
  • schottky barrier
  • electron mobility
  • operating temperatures
  • device physics

  • microwave devices
  • threshold voltages
  • semiconductor field
  • device technologies
  • operating temperature

  • calculated reverse
  • generation current
  • sic digital
  • pen junctions
  • saturated velocity


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