Lecture on Charge Carriers: Electrons and Holes

Key Concepts

Types of Charge Carriers

• Electrons: Negatively charged particles
• Holes: Absence of an electron, acts as a positively charged particle

Direction of Current

• Conventional Current: Opposite to the direction of electron flow
  • If electrons flow left to right, current flows right to left
• Natural Current: Same direction as the flow of electrons
  • If electrons flow left to right, natural current also flows left to right

Hole as Charge Carrier

• In a silicon lattice doped with boron (trivalent impurity), holes act as charge carriers
• Movement of holes:
  • Neighboring electrons fill the holes, creating new holes where the electrons were
  • This movement appears as if the hole is moving through the lattice
• Example of hole movement:
  • Initial hole position → neighboring electron fills the hole → new hole at the electron's previous position
• Holes move in the same direction as the conventional current

Detailed Explanation

Hole Movement in Silicon Lattice

1. A hole exists in the lattice.
2. A neighboring electron moves to fill the hole.
3. A new hole is created where the electron was originally.
4. This process continues, causing the hole to appear to move through the lattice.
5. The movement of holes is from right to left (same as conventional current).

Implications

• The movement of holes in the lattice shows that they contribute to the flow of current in semiconductors.
• Understanding both electron and hole movements is crucial for analyzing current flow in semiconductor devices.

Summary

• Electrons flow opposite to conventional current.
• Holes move in the same direction as conventional current and contribute to the overall current flow in semiconductors.

Q&A

• Leave any questions in the comment section for further clarification.