XII.XIV Semiconductor Electronics: Material, Devices And Simple Circuits

The energy band structure in solids may be classified in four broad types as shown in figure. The gap between the top of valence band and bottom of conduction band is called the energy gap.

In a pure semiconductor (intrinsic semiconductor), number of conduction electrons and holes is equal.

Semiconductor with an impurity doped into it is called extrinsic semiconductor

• n-type semiconductor (doped with pentavalent)
• p-type semiconductor (doped with trivalent)

The conductivity of a semiconductor increases as the temperature is increased, as more electrons cross the energy gap and number of electron holes pair increases.