Dissemination of IT for the Promotion of Materials Science (DoITPoMS)

DoITPoMS Teaching & Learning Packages Introduction To Semiconductors Questions
Introduction To Semiconductors AimsBefore you startIntroductionIntroduction to Energy BandsThe Fermi–Dirac DistributionCharge Carriers in SemiconductorsIntrinsic and Extrinsic SemiconductorsDirect and Indirect Band Gap SemiconductorsCompound SemiconductorsBehaviour of the Chemical PotentialMetal–Semiconductor Junction – Rectifying ContactMetal–Semiconductor Junction – Ohmic ContactThe p–n JunctionBipolar TransistorMetal Oxide Semiconductor Field Effect Transistor (MOSFET)SummaryQuestionsGoing further
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Questions

Quick questions

You should be able to answer these questions without too much difficulty after studying this TLP. If not, then you should go through it again!

  1. What are the majority carriers of electric current in B-doped Si?

    a Holes
    b Electrons
    c Boron ions
    d Silicon atoms

  2. At absolute zero, which of these statements describes the position of the chemical potential in an n-type semiconductor?

    a It is between the top of the valence band and the acceptor levels.
    b It is in the middle of the band gap.
    c It is between the middle of the band gap and the bottom of the conduction band.
    d It is between the middle of the band gap and the top of the valence band.
    e It is between the the donor levels and the bottom of the conduction band.

  3. At room temperature, which of these statements describes the position of the chemical potential in an n-type semiconductor?

    a It is between the top of the valence band and the acceptor levels.
    b It is in the middle of the band gap.
    c It is between the middle of the band gap and the bottom of the conduction band.
    d It is somewhere between the middle of the band gap and the top of the valence band.
    e It is at the same energy level as the donor energy levels.

  4. Which of the following junctions is not rectifying?

    a Metal - p-type semiconductor contact where ΦM < ΦS.
    b p-n junction
    c Metal - p-type semiconductor contact where ΦM > ΦS.
    d Metal - n-type semiconductor contact where ΦM > ΦS.

  5. The work function of gold is 4.8 eV and the electron affinity of silicon is 4.05 eV. Silicon has a band gap of 1.12 eV at 300 K. What is the barrier height at 300 K preventing the majority carriers in n-type silicon from crossing between a piece of n-type silicon and gold where the chemical potential of the n-type silicon is 0.25 eV below the bottom of the conduction band?

    a 0.75 eV.
    b 0.5 eV.
    c 1.12 eV.
    d 4.05 eV.
    e 0.25 eV.

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