# Um, i'm having a hard time understanding some terms and equations in

1. Jun 13, 2010

### chemic_23

um, i'm having a hard time understanding some terms and equations in semiconductors, particulary 2 equations and 1 term(fermi function,density of state function, and fermi level). My understanding of fermi function is somewhat the probability of an energy state to be occupied by an electron. for the density of energy state function, it is the number of energy state available for the conduction band to be filled with electron. and for the fermi level, i dont really understand why the probability of occupancy by an electron is 50% or 1/2.Are these notions correct? would someone kindly explain clearly what is fermi function,fermi level,density of state function? and why does fermi level have 50% probability? and also, are these only applicable to semiconductors? or conductors and insulators are also included? thanks:)

2. Jun 13, 2010

### muh_j18

Re: semiconductors

under equilibrium conditions (no external voltages or electric fields are acting on the semi cmnducotr), the electrons accomulate under a specific energy level, and they do not have enough energy to raise up this levelm this level is called the fermi level.
the probability of occubation of a certain energy level is given by:
f=1/(1+e^((E-Ef)/(KT))
where T is the temerature, K is Boltzman's constant, and Ef is the fermi level.
if you substitute Ef in place of E, you get the probability of occubation of the fermi level which is 1/2.