Semiconductor Theory
Semiconductors Definition : The materials, whose electrical conductivity lies between those of conductors and insulators and have negative temperature coefficient of resistance, are known as semiconductors. Semiconductor Materials : The few examples of semiconductor materials are as under : 1.Carbon (C) 2. Silicon (Si) 3.Germanium (Ge) 4. Selenium (Se) 5.Gallium Arsenide (GaAs) 6.Cadmium Sulphide (CdS). The commonly used semiconductor materials are Germanium and Silicon. These are tetravalent elements i.e. materials having four valency. Atomic Structures of Germanium and Silicon : (i) Atomic structure of Germanium and Silicon atoms : Fig. 1.3 (b) shows the atomic structure of a Germanium atom in which first, second, third and fourth orbits have 2, 8, 18 and 4 electrons respectively, with the result that the atomic number for Germanium is 32. Fig. 1.3 (a) shows the atomic structure of a Silicon atom in which first, second and th