What is a semiconductor ?

A semiconductor is a material with electrical conductivity that falls between that of a conductor (like metals) and an insulator (like rubber). This intermediate conductivity can be modified and controlled, making semiconductors essential in modern electronics.

Key Properties of Semiconductors:

  1. Conductivity Control: Their conductivity can be adjusted by introducing impurities (a process called doping) or by external factors such as temperature, light, or electric fields.
  2. Band Gap: Semiconductors have a specific energy gap (band gap) between their valence band (where electrons are bound to atoms) and conduction band (where electrons can move freely). Electrons need enough energy to jump this gap to conduct electricity.
  3. Temperature Sensitivity: Unlike metals, semiconductors become better conductors as their temperature increases.
  4. Types of Charge Carriers: Semiconductors conduct electricity via two types of charge carriers:
    • Electrons (negative charge).
    • Holes (positive charge, representing the absence of an electron).

Types of Semiconductors:

  1. Intrinsic Semiconductors: Pure semiconductors, such as silicon or germanium, where conductivity depends solely on temperature and intrinsic properties.
  2. Extrinsic Semiconductors: Doped semiconductors that have added impurities to increase conductivity:
    • n-type: Extra electrons (negative charge carriers) are added.
    • p-type: Extra “holes” (positive charge carriers) are created.

Common Semiconductor Materials:

  • Silicon (Si): The most widely used material in electronics.
  • Germanium (Ge): Used in some high-speed devices.
  • Gallium arsenide (GaAs): Used in high-frequency and optoelectronic devices.

Applications:

Semiconductors are the foundation of modern technology and are used in devices such as:

  • Transistors
  • Diodes
  • Integrated Circuits (ICs)
  • Solar Cells
  • LEDs
  • Sensors

The ability to precisely control electrical properties makes semiconductors critical for everything from computers and smartphones to renewable energy and advanced medical equipment.