The document discusses energy band gaps in materials. It provides information on the density of electrons, energy gaps, and electric fields required for insulators, semiconductors, and metals. It then lists common materials used in semiconductors along with their band gap energies in electronvolts at 302 Kelvin. These include diamond, silicon dioxide, silicon, germanium, and lead sulfide. The document also discusses silicon-germanium alloys and intrinsic semiconductors. It covers doping, p-n junction diodes, their uses as electronic switches and rectifiers. Transistors are discussed for their uses as amplifiers, oscillators, and in integrated circuits. Radio broadcasting and reception is also mentioned

1. Energy Band Gap in Materials

2. Property Insulator
Semi-
conductor
Metal
Density of
electrons
10 7 met -3 10 17 met -3 10 28 met -3
Energy gap > 3 ev
0.5 ev –
1.5 ev
Almost Nil
Electric
Field
required
10 8 vol/mtr 300 0 Kelvin
Any small
voltage

3. Name of the
substance
Symbol
Energy Gap in
eV at 302 K
Diamond C 5.5 eV
Silicon di
Oxide
Si O2 9 eV
Silicon Si 1.11 eV
Germanium Ge 0.67 eV
Lead Sulphide Pb S 0.37 eV

4. SiliconGermaniumIntrinsic semiconductors

5. Hole & Free Electron

6. Hole

8. I = I (hole) + I (electron) = 2 I

9. doping
The process of
introducing impurities
in small quantities
in to a material is
called “doping”.

10. Doping Materials

15. Junction Diode

17. Junction diode in forward bias

18. Junction diode in reverse bias

19. Uses of p-n Junction Diode
•Electronic switch
•Rectifier
•L E D s

25. Uses of Transistors
• It acts as an amplifier
• It acts as an oscillator
• Used as stabilizers in power
supplies
• Important components in ICs
or CHIPs.

26. Radio Broadcasting and Reception