SEMICONDUCTORS In recent years there have been remarkable advances in technology that have revolutionized telecommunications, computing, and information storage and retrieval. Devices such as field effect transistors, integrated circuits, microprocessors, and electromagnetic radiation detectors and emitters have played key roles in this revolution. In large measure these devices are based on semiconductor science.
Semiconductors are distinguished from other materials by certain physical properties. Solid semiconductors appear as crystalline or amorphous form. Crystalline being the most important manifestation of semiconductors is the state in which atoms or ions are arranged in a periodic array in an ordered state. Crystalline form semiconductors exhibit perfectly regular three-dimensional arrangements of atoms making up the solid over many hundreds or thousands of atomic radii. In the amorphous form the ions are arranged in a disordered state. The positions of ions and atoms in an amorphous state unlike crystalline's 3D arrangement are in a state of randomness.
One of the most important traits of semiconductors is the electric resistivity or the difficulty with which an electric current can pass through the material under the influence of an electric field. Though materials may be classified into three categories: insulators, for which the resistivity is very high; metals, for which the resistivity is very low; and semiconductors, for which the resistivity is intermediate in value and highly temperature dependent. An important property of semiconductors is the ability to change their resistivity over several orders of magnitude by doping. It is used for diodes, transistors, integrated circuits, memories, infrared detection and lenses, light-emitting diodes (LED), photo sensors, strain gages, solar cells, charge transfer devices, radiation detectors and a variety of other devices. Elemental semiconductors are simple-element semiconductor materials such as silicon or germanium.
The production of devices based on semiconducting materials involves a series of processes. The primary process...