Extrinsic Semiconductor

1. Extrinsic Semiconductor
P Type

2. • Trivalent elements added to the intrinsic semiconductor
• Eg - Al, Ga or Indium have three electrons in their outer most
orbits
• Three electrons are engaged in covalent bonding with the three
neighboring Si atoms.
• Indium needs one more electron to complete its bond.
• This electron maybe supplied by Silicon , there by creating a
vacant electron site or hole on the semiconductor atom.
• Indium accepts one extra electron
• The energy level of this impurity atom is called acceptor level and
this acceptor level lies just above the valence band.
• These type of trivalent impurities are called acceptor impurities
• The semiconductors doped with the acceptor impurities are called
P-type semiconductors.
Extrinsic Semiconductors
P type

3. Si
Si
Si
In
Si
Impure atom
(acceptor)
Extrinsic Semiconductors
P type

4. Si
Si
Si
In
Si
Co-Valent
bonds
Impure atom
(acceptor)
Extrinsic Semiconductors
P type

5. Si
Si
Si
In
Si
Hole
Co-Valent
bonds
Impure atom
(acceptor)
Extrinsic Semiconductors
P type

6. E
Ev
Valence band
Ec
Conduction band
Ec
Electron
energy
Distance
Eg
Extrinsic Semiconductors
P type

7. E
Ea
Ev
Valence band
Ec
Conduction band
Ec
Electron
energy
Distance
Acceptor levels
Eg
Extrinsic Semiconductors
P type

8. • At relatively low temperatures, the
acceptor atoms get ionized.
Extrinsic Semiconductors
P type

9. • At relatively low temperatures, the acceptor atoms get
ionized.
• Taking electrons from valence band.
Extrinsic Semiconductors
P type

10. • At relatively low temperatures, the acceptor atoms get
ionized.
• Taking electrons from valence band.
• Giving rise to holes in valence band
for conduction.
Extrinsic Semiconductors
P type

11. • At relatively low temperatures, the acceptor atoms get
ionized.
• Taking electrons from valence band.
• Giving rise to holes in valence band for conduction.
• Due to ionization of acceptor atoms
only holes and no electrons are
created.
Extrinsic Semiconductors
P type

12. • At relatively low temperatures, the acceptor atoms get
ionized.
• Taking electrons from valence band.
• Giving rise to holes in valence band for conduction.
• Due to ionization of acceptor atoms only holes and no
electrons are created.
• Thus holes are more in number than
electrons.
Extrinsic Semiconductors
P type

13. • At relatively low temperatures, the acceptor atoms get
ionized.
• Taking electrons from valence band.
• Giving rise to holes in valence band for conduction.
• Due to ionization of acceptor atoms only holes and no
electrons are created.
• Thus holes are more in number than electrons
• Holes are majority carriers and
electrons are minority carriers in P-
type semiconductors.
Extrinsic Semiconductors
P type

14. • At relatively low temperatures, the acceptor atoms get
ionized.
• Taking electrons from valence band.
• Giving rise to holes in valence band for conduction.
• Due to ionization of acceptor atoms only holes and no
electrons are created.
• Thus holes are more in number than electrons
• Holes are majority carriers and electrons are minority
carriers in P-type semiconductors.
Extrinsic Semiconductors
P type