CHEMISTRY - BAND GAP TO EXPLAIN CONDUCTORS ,INSULATORS AND SEMICONDUCTORS

B TECH

COMPUTER SCIENCE ENGINEERING

CHEMISTRY(BTCH101-23)

TOPIC- BAND GAP TO EXPLAIN
CONDUCTORS,SEMICONDUCTORS AND INSULATORS
IMPORTANT TERMS:-
●​ VALENCE BAND: The energy level occupied by the valence electrons is known as the
valence band. ​

●​ CONDUCTION BAND: The energy level above the valence band is known as the
conduction band. It is the band in which electrons go after excitation. ​

●​ FORBIDDEN GAP: The gap between the valence band and conduction band is known as
the forbidden band gap. ​


Depending upon the band gap, solids are classified into three categories:


●​ Conductors ​

●​ Semiconductors ​

●​ Insulators ​


Conductors:
●​ The energy gap between the conduction band and valence band is almost negligible. ​

●​ With an increase in temperature, the conductivity of metal decreases. ​

●​ Examples: copper and silver. ​


Insulators:
●​ The band gap between the valence band and conduction band is almost 5 to 10 eV. ​

, ●​ Here, the conductivity increases with an increase in temperature. ​

●​ Examples: Diamond and glass. ​


Semiconductors:
●​ The energy gap is almost 1 eV, which is an intermediate gap between metals and
insulators. ​

●​ Here, conductivity increases with an increase in temperature. ​

●​ Examples: Germanium and Silicon. ​




The following table illustrates the band structures:

●​ Conductors: CB (Conduction Band) and VB (Valence Band) are overlapping. ​

●​ Insulators: CB and VB are separated by a large band gap. ​

●​ Semi-conductors: CB and VB are separated by a small band gap.




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Semiconductors are of two types:

●​ Intrinsic semiconductors ​