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fermi level

Discussion in 'Electronics Homework Help' started by bhuvanesh, Jan 21, 2015.

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  1. bhuvanesh


    Aug 29, 2013
    what is mean by number of states and what is mean by occupancy(i think they are taking about fermi level.but i am very clear what is fermi level )

    some one help please.Thank you in advance
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    It's been some time I had to deal with these details of semiconductor physics. Here's what I think I still understand:

    In a block of material no two electrons can have the same state (Pauli exclusion principle). Therefore for a meterial to be able to accomodate a given number of electrons the material has to provide a set of different states, one for each electron. The total number of possible states is given by N(E).
    Not every state is occupied by an electron, however. The ratio of occupied states to total number of states is the occupancy.

    To calculate the effective numbe rof electrons in any band you multiply the total number of states (max. possible number of electrons) by the ratio of occupied states to total number of states (F(E)) and integrate this number over the respective band (here: conduction band).
  3. Arouse1973

    Arouse1973 Adam

    Dec 18, 2013
    Harald you do always impress me. Thats very good.
  4. Ratch


    Mar 10, 2013
    They are talking about the Fermi function, which uses the Fermi level as one of its parameters. You have stated that you clearly know what the Fermi level is. The Fermi function is a probability distribution function of how many of the existing states will be filled with an electron. The density of states tell how many states exist at a particular energy level. The distribution of electrons is the density of states at each energy level multiplied by the Fermi function at each energy level.

    Harald Kapp and Arouse1973 like this.
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