Basics of Semiconductors

Introduction

Semiconductors have become central in electronics, replacing vacuum tubes.
Advantages of semiconductors over vacuum tubes:
- More efficient
- Require less space and lower operating voltage

Materials that are intermediate in electrical conductivity between conductors and insulators.
Common semiconductor materials:
- Silicon: Most commonly used
- Gallium Arsenide: Second most common
- Germanium: Previously used, less stable at high temperatures

Have two current carriers: free electrons and holes.
Free electrons are created when thermal energy allows valence electrons to jump to the conduction band.
Holes are vacancies left in the valence band when electrons move to the conduction band.
Intrinsic semiconductors have equal numbers of free electrons and holes, but low conductivity.

Definition: Process of adding impurities to increase semiconductor conductivity.
Types of Doping:
- N-type Semiconductors
  - Created by adding pentavalent impurity atoms (e.g., phosphorus, arsenic).
  - Increases number of free electrons.
- P-type Semiconductors
  - Created by adding trivalent impurity atoms (e.g., boron, indium).
  - Increases number of holes.
Process Overview:
- N-type: Adding an atom with five valence electrons leaves one extra electron.
- P-type: Adding an atom with three valence electrons creates a hole where an electron is missing.

Created by placing p-type and n-type materials adjacent to one another.
Forms the basis for semiconductor devices like diodes, transistors, and thyristors.

Semiconductors replaced vacuum tubes due to better efficiency and lower voltage requirements.
Doping is essential for increasing semiconductor conductivity and forming electronic components.
P-N junctions are fundamental in creating semiconductor devices.