ABSTRACT
The active devices in nearly all VLSI circuits are made from the semiconductor silicon. In this single-crystal material, all the valence electrons take part in covalent bonding so the intrinsic conductivity is low. However, the introduction of impurities in trace quantities allows the control of the conductivity and the realization of junctions and transistors, the building blocks of digital integrated circuits. This chapter reviews the physical and electrical properties of silicon as well as the physics of p-n junctions. Silicon crystallizes in the diamond structure are shown. The unique properties of semiconductors result from the fact that the allowed energy levels of electrons exist in bands that are separated by forbidden gaps. With all electrons covalently bonded, there are no free carriers to participate in electrical conduction unless some of the bonds are broken, either thermally, or by illumination with light, or by doping.
