Semiconductor physics

What type of band structure does silicon have?

  1. ADirect band gap
  2. BIndirect band gap
  3. CMetallic, with no band gap
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Answer: B. Indirect band gap

Silicon is an indirect-band-gap semiconductor: the bottom of the conduction band and the top of the valence band are at different wave numbers. Because radiative recombination requires the involvement of lattice vibrations (phonons), light emission is very inefficient, so direct-gap materials such as GaAs are used for LEDs and lasers.

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More Semiconductor physics questions

  1. What can be learned from a Hall effect measurement?
  2. What is a semiconductor called whose impurity concentration is so high that the Fermi level lies inside the conduction or valence band?
  3. Which is the Einstein relation between the diffusion coefficient D and the mobility μ of carriers? (k: Boltzmann constant, T: absolute temperature, q: elementary charge)
  4. Which value is closest to the thermal voltage kT/q at room temperature (300 K)?
  5. Where in the band gap is the donor level created by phosphorus in silicon?