The document discusses p-type semiconductors. Trivalent impurity atoms like indium are added to an intrinsic semiconductor like silicon. These impurity atoms have three outer electrons that bond with silicon atoms, leaving the impurity atom with one less electron than normal. This causes the impurity atom to act as an electron acceptor from the silicon, leaving a hole where the electron was. At low temperatures, the acceptor atoms become ionized by taking electrons from the valence band and creating holes for conduction. As a result, holes become the majority carriers in p-type semiconductors rather than electrons.

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