Carriers

A Brief Description
Definitions
What are they?
 Creating Carriers with Dopants
Density of States An Analogy The Fermi Function Where are they?
How many are there?
 Charge?
Effects of Temperature
 Related Topics

Carrier Distribution

We need to know how many electrons and holes there are in a semiconductor.  Sometimes we also need to know which energy levels they are typically occupying.  Taking what we know of the density of states (the distribution of the energy states in the energy bands) and the Fermi function (the probability of an energy state being occupied by an electron) we can determine the distribution of the carriers.  This is simply done by multiplying the two functions for the respective energy band.  The distribution of electrons in the conduction band can be found by the product gc(E)f(E).  The distribution of holes in the valence band can be found by the product gv(E)[1-f(E)].

At the band edges g(E) dominates and the carrier distribution is zero.  As we move up in energy, f(E) dominates in the conduction band and will approach zero as the probability of an energy state being occupied approaches zero.  [1-f(E)] dominates in the valence band and will approach zero as the probability of an energy state being empty approaches zero.

Next Concept: 
 Carrier Concentrations
Previous Concept: 
 The Fermi Function
Back: 
 Fundamentals