ABSTRACT
This chapter presents elementary physics of spatially uniform semiconductors in equilibrium. Electron orbitals in an atom have discrete energy levels, whereas those in a large crystal are band-like with continuously distributed energy levels. Electron and hole densities of a semiconductor are determined by the effective densities of states, Nc and Nv, respectively, which are material constants, and the Fermi level ζ, which depends on impurity doping. The Fermi level Ei of an intrinsic semiconductor is located at around the middle of the forbidden band. For n-type semiconductors, the Fermi level lies above the intrinsic Fermi level, and for p-type semiconductors, it lies below. The Fermi level is the electrochemical potential of electrons in solids. The electrochemical potential of an electrically charged gas is determined by the density of gas particles and the electrostatic forces acting on the particles.
