ABSTRACT
In this chapter, fundamental concepts such as the Fermi level, the surface dipole, the chemical potential, and the Volta and Galvani potentials will be defined and discussed with examples. In this chapter, these concepts are described in total equilibrium conditions, but they form the basis for the description of nonequilibrium phenomena such as the diffusion flux. The electrons in the semiconductor crystal will be distributed in different states labeled by momentum and spin. According to Pauli principle, two electrons, which have spin 1/2, cannot occupy the same quantum state. In between carrier relaxation and recombination timescales, an important time span occurs in which carriers can be considered relaxed to equilibrium distribution into the respective band. Therefore, the excess population of each type of carrier spreads over the respective energy levels according to the equilibrium functions.
