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Figure 14.2 Covalent bonding of silicon atoms by sharing of valence electrons, for ease of
understanding only the outermost orbit of each silicon atom has been shown. The inner two orbits have
been omitted.
14.4 EXTRINSIC SEMICONDUCTORS
The process of adding either a pentavalent element or a trivalent element to a
pure semiconductor is called doping. The doped semiconductor is called
extrinsic semiconductor. The doping material that is added to a pure
semiconductor is also referred to as impurity material. Depending upon
whether a pentavalent or trivalent doping material is added, extrinsic
semiconductors are respectively called n-type semiconductor or p-type
semiconductors. These two types of materials when joined together form, a
p–n junction which is the basis of working of all the electronic devices. The
students are advised to understand the mechanism of working of a p–n
junction so as to understand the functioning of all electronic devices and
circuits.
14.4.1 N-Type Semiconductor Material
