It was lesson prepared to present chapter "SEMICONDUCTORS" for SSC students in previous syllabus

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