OVERVIEW

In the preceding chapter on solid properties, we relied on the Drude-Sommerfeld model, which assumes that electrons are completely free and the Fermi surface is spherical and isotropic in all directions of the wavevector. While the concepts of electronic band structures and phonon dispersion in real solids were often mentioned, we have deliberately avoided any details. It is hoped that the free-electron model will help readers gain an intuitive picture of electrons without a deep knowledge of solid state physics. Note that the freeelectron model is applicable only for metals, usually good conductors, and cannot be applied to semiconductors. The Sommerfeld theory, albeit successful in quantitatively describing electronic transport for certain metals, does not touch on the fundamental mechanisms of electron scattering and the shape of the Fermi surface. The free-electron model also fails to explain certain phenomena including thermoelectricity. The Hall effect and magnetoresistance, to be discussed in the following section, provide further evidence of the inadequacy of the free-electron model.

This chapter introduces electronic band theory after a brief discussion of electronic structures in atoms, binding in crystals, and crystal lattices. The phonon dispersion relations are presented subsequently and explained in terms of different branches of acoustic and optical phonons. Subsequently, the electron and phonon scattering mechanisms are explored. The next section addresses electronic emission and tunneling phenomena, including photoelectric effect, thermionic emission, field emission, as well as electron tunneling through a potential. A significant portion of this chapter is then devoted to semiconductor materials and devices,...