TABLE OF CONTENTS The energy band model is a rather involved one in solid-state physics. Here we only summarize some of its basic features for interested readers. More details can be found in the references provided in Chap. 1. The following material can be understood in the context of Sec. 1.2.
For semiconductors, the energy band model can be illustrated as shown in Fig. A.1. The horizontal axis corresponds to distance in the semiconductor, whereas the vertical axis corresponds to electron energy. In an intrinsic semiconductor, electrons bound to their parent atom have energy no larger than E v; they are said to "be in the valence band." An electron with a total energy of at least E c becomes liberated from the parent atom and is said to "be in the conduction band." Such an electron leaves "behind" a hole in the valence band. The energy of holes is measured in a direction opposite from that of electrons because of their opposite charge (i.e., hole energy increases downward in Fig. A.1). If an electron acquires a total energy E > E c (e.g., because of thermal vibration of the lattice), the difference E ? E c corresponds to net kinetic energy as the electron moves in the crystal lattice. E c itself represents the potential energy of the free electron. Energy levels between E v and E c are not occupied in the intrinsic semiconductor under discussion. Such energies belong...
