Semiconductor, Types of Semiconductor
Semiconductors are materials whose electrical properties lie between Conductors and Insulators.
Ex : Silicon and Germanium
semiconductor = material for which gap between valence band and conduction band is small; (gap width in Si is 1.1 eV, in Ge 0.7 eV).
at T = 0, there are no electrons in the conduction band, and the semiconductor does not conduct (lack of free charge carriers);
at T > 0, some fraction of electrons have sufficient thermal kinetic energy to overcome the gap and jump to the conduction band; fraction rises with temperature;
e.g. at 20o C (293 K), Si has 0.9x1010 conduction electrons per cubic centimeter; at 50o C (323 K) there are 7.4x1010 .
Types of Semiconductor
Intrinsic semiconductors
Extrinsic (doped) semiconductors
n-type materials
p-type materials