Semiconductor physics

Which is a typical factor that shortens the minority carrier lifetime in silicon?

  1. AImpurities that create deep levels, such as gold, and crystal defects
  2. BCooling the wafer to cryogenic temperatures
  3. CPlacing the wafer in a vacuum
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Answer: A. Impurities that create deep levels, such as gold, and crystal defects

Heavy-metal impurities such as gold and iron, and crystal defects, create deep levels near the middle of the band gap that act as recombination centers, promoting electron-hole recombination. This shortens the minority carrier lifetime. In fast-switching diodes, heavy metals are sometimes added deliberately, or electron irradiation is used, to shorten the lifetime.

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More Semiconductor physics questions

  1. What is the crystal structure of single-crystal silicon?
  2. What is the drift velocity of electrons with a mobility of 1000 cm²/V·s in an electric field of 100 V/cm?
  3. What is the mass introduced so that the motion of an electron in a crystal can be treated like that of a free electron in response to external forces?
  4. What does the Fermi level mean?
  5. What is the approximate hole density in n-type silicon with a donor concentration of 1×10¹⁶ cm⁻³ (all donors ionized, intrinsic carrier density ni = 1×10¹⁰ cm⁻³)?