Classification of Semiconductors – Class 12 | Chapter – 14 | Physics Short Notes Series PDF for NEET & JEE

Classification of Semiconductors: Semiconductors are materials that have electrical conductivity between that of a conductor and an insulator. They have a band gap, which is the energy difference between the valence band (the highest energy band occupied by electrons) and the conduction band (the lowest energy band available for electrons to move into). This band gap determines the material’s ability to conduct electricity.

In pure form, semiconductors are poor conductors of electricity, but they can be made to conduct by adding impurities, a process called doping. Doping introduces impurity atoms into the semiconductor crystal, which either donate or accept electrons, creating excess or deficient electrons, respectively. This creates regions of excess and deficient electrons in the material, known as p-type and n-type regions. When a p-type region and an n-type region are joined together, it forms a p-n junction, which is the basis of most semiconductor electronic devices.

Classification of Semiconductors

Classification of Semiconductors are based on various criteria, such as their composition, crystal structure, doping, and band gap. Here are some common classification of semiconductors:

  • Elemental semiconductors: Elemental semiconductors are made up of a single element, such as silicon (Si), germanium (Ge), and tin (Sn). Silicon is the most commonly used semiconductor material and is the basis of modern electronics.
  • Compound semiconductors: Compound semiconductors are made up of two or more elements, such as gallium arsenide (GaAs), indium phosphide (InP), and aluminum gallium arsenide (AlGaAs). Compound semiconductors have higher electron mobility and are used in applications that require high-speed electronic devices.
  • Organic semiconductors: Organic semiconductors are made up of organic molecules, such as polymers and small molecules. They are used in applications such as organic light-emitting diodes (OLEDs) and organic photovoltaics.
  • Amorphous semiconductors: Amorphous semiconductors do not have a well-defined crystal structure, unlike elemental and compound semiconductors. They are used in applications such as thin-film solar cells and liquid crystal displays.
  • Doped semiconductors: Doped semiconductors are semiconductors that have impurities added to them, which changes their electrical properties. There are two types of doped semiconductors: p-type, which have excess holes, and n-type, which have excess electrons. Doped semiconductors are used in applications such as diodes, transistors, and integrated circuits.
  • Wide bandgap semiconductors: Wide bandgap semiconductors have a larger bandgap than traditional semiconductors, which makes them useful in high-power and high-frequency electronic devices. Examples include silicon carbide (SiC) and gallium nitride (GaN).

These are some common classification of semiconductors based on their properties and characteristics. The classification of a semiconductor depends on the materials and conditions under which it is used, and different classifications may overlap depending on the specific application.

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