Electron hole pairs, semiconductor theory

Discussion in 'Homework Help' started by Michael Lake, Oct 30, 2015.

  1. Michael Lake

    Thread Starter New Member

    Oct 29, 2015
    2
    0
    hi :)

    im a first year mechactronics student and ive noticed one particular question that always come up the in the tests. ive googled for the answer and i get multiple different answers.

    the question is as follows:
    Electron hole pairs are made by...
    a) doping b)thermal energy c) ionisation d) covalent bonding

    this question originates from the semiconductor theory chapter in my course.
    i think the answer is b
     
  2. RBR1317

    Active Member

    Nov 13, 2010
    232
    48
    That sounds like a trick question. I think I would rephrase the question to ask, The absence of what item in the list would mean there are no holes?
     
  3. Michael Lake

    Thread Starter New Member

    Oct 29, 2015
    2
    0
    ok so if its asked the way you put it what answer would you give?
     
  4. Papabravo

    Expert

    Feb 24, 2006
    10,179
    1,800
    A brick of pure semiconductor has no electron-hole pairs regardless of the level of thermal energy. It is also true that the atoms in a brick of pure Silicon have covalent bonds to their neighbors in the crystal lattice.
     
  5. bertus

    Administrator

    Apr 5, 2008
    15,649
    2,348
  6. RBR1317

    Active Member

    Nov 13, 2010
    232
    48
    The most useful concept for explaining conduction in solids is the energy band model. In a semiconductor the electrons normally occupy the valence band but can jump to the conduction band if they absorb enough energy to overcome the band gap energy. When an electron jumps to the conduction band, it leaves behind a hole, thereby forming an electron-hole pair. Holes are the electron voids in the valence band. Thermal energy can cause an electron to jump the band gap but it is not the only source of energy capable of doing so. Note that this energy band model can apply to pure semiconductors. When applied to doped semiconductors, the explanation becomes somewhat more 'interesting'.
     
Loading...