Fundamentals of Semiconductor Physics

Sep 30, 2024

Overview of Semiconductor Physics

Introduction

  • Focus on semiconductor physics for electrical engineers
  • Key questions addressed in lecture:
    • How many charge carriers are available?
    • Where are they and how do they move?
    • How can we change them and create useful applications?

Central Questions in Semiconductor Physics

  1. Charge Carriers

    • Definition: Charge carriers such as electrons in semiconductors.
    • Difference from metals: In metals, the number of conducting electrons is roughly equal to the number of atoms, but this is not the case in semiconductors.

  2. Carrier Movement

    • Understanding how charge carriers respond to external electric fields.
    • Considering charge concentration changes and effects over time.

  3. Applications

    • Analyzing devices like MOSFETs, diodes, and BJTs.
    • Emphasis on practical engineering applications of semiconductor physics.

Roadmap of the Course

  • Start with Quantum Mechanics and Statistical Mechanics (STATMEC).
  • Key tools will include:
    • Conservation laws
    • Density of states
    • Energy momentum band diagrams

Key Concepts to be Covered

  • Density of States: How many states electrons can occupy in semiconductors, indicating available room for electrons.
  • Energy Band Diagram: Fundamental to understanding semiconductor physics.
  • Effective Mass: Relating charge movement in free space to movement in semiconductors.
  • Fermi Statistics: Tied to density of states to determine the number of charge carriers.

Charge Carriers and Their Nature

  • Use of the term "charge carriers" includes electrons and holes (positively charged counterparts to electrons).

Mechanisms of Movement

  • Underlying theories: Maxwell’s equations and probability theory.
  • Carrier movement driven by:
    • Drift: Movement due to electric fields.
    • Diffusion: Movement due to concentration gradients.
  • Carrier generation and recombination: Continuous creation and destruction of carriers.

Connection to Ohm's Law

  • Understanding carrier drift leads directly to deriving Ohm's law, bridging circuit theory and semiconductor physics.

Advanced Concepts

  • Continuity Equation and Ambipolar Transport Equation:
    • Tools for analyzing semiconductor problems, especially p-n junctions.
    • Application in understanding diodes, MOSFETs, BJTs, and optical devices (solar cells, LEDs).

Conclusion

  • The overview serves as a foundation for deeper understanding.
  • Upcoming video will begin with Quantum Mechanics, the first topic in the series.