P-type and N- Type Semiconductors

 

Semiconductors are materials that have electrical conductivity between conductors (like metals) and insulators (like nonmetals). The behavior of semiconductors can be further classified into two major types: P-type and N-type semiconductors.

P-type Semiconductor:

A P-type semiconductor is created by adding a small amount of a trivalent impurity (such as boron, aluminum, or gallium) to a pure semiconductor material (like silicon or germanium). This addition introduces "holes" in the crystal lattice, creating electron deficiencies.

- Doping Process:

  - For instance, consider silicon (Si) as the base semiconductor material.

  - Boron (B), which has three valence electrons, replaces some silicon atoms in the crystal lattice. As a result, one electron is missing (creating a hole) for each boron atom introduced.

- Electron Deficiency (Holes):

  - These holes, or vacant positions in the crystal lattice, effectively behave like positive charge carriers.

- Electrical Conductivity:

  - In a P-type semiconductor, the majority charge carriers are holes, while a small number of electrons contribute to conductivity.

N-type Semiconductor:

An N-type semiconductor is created by adding a small amount of a pentavalent impurity (such as phosphorus, arsenic, or antimony) to the same pure semiconductor material.

- Doping Process:

  - Using silicon (Si) again as the base material.

  - Phosphorus (P), which has five valence electrons, replaces some silicon atoms. The extra electron introduces additional free electrons in the crystal lattice

- Excess Electrons:

  - These extra electrons, beyond those needed for covalent bonds, become the majority charge carriers in the semiconductor.

- Electrical Conductivity:

  - In an N-type semiconductor, the majority charge carriers are electrons, while there are also holes present due to the absence of electrons at some lattice sites.

 

Summary:

- P-type Semiconductors:

  - Doped with trivalent impurities.

  - Majority carriers: Holes.

  - Minority carriers: Electrons.

- N-type Semiconductors:

  - Doped with pentavalent impurities.

  - Majority carriers: Electrons.

  - Minority carriers: Holes.

 Applications:

- P-N Junctions:

  - The combination of P-type and N-type semiconductors forms the basis of diodes, transistors, and other semiconductor devices by creating P-N junctions with distinct electrical properties.