Question:

Conductivity of silicon increases by doping it with group-15 elements. Doping means introduction of small amount of impurities like $P, As$ or $Bi$ into the pure crystal.

Updated On: Jul 28, 2022
  • If both assertion and reason are true and reason is the correct explanation of assertion
  • If both assertion and reason are true but reason is not the correct explanation of assertion
  • If assertion is true but reason is false
  • If both assertion and reason are false
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The Correct Option is B

Solution and Explanation

When a silicon crystal is doped with a group-15 elements, such as $P, A s, S b$ or $B i$ the structure of the crystal lattice is left unchanged but an occasional atom with five valence electrons occupies a site that would normally be occupied by a silicon atom. The foreign atom uses four of its electrons in covalent bonding but the remaining fifth electron becomes delocalised and is thus free to contribute to electrical conduction.
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Concepts Used:

Solid State

Solids are substances that are featured by a definite shape, volume, and high density. In the solid-state, the composed particles are arranged in several manners. Solid-state, in simple terms, means "no moving parts." Thus solid-state electronic devices are the ones inclusive of solid components that don’t change their position. Solid is a state of matter where the composed particles are arranged close to each other. The composed particles can be either atoms, molecules, or ions. 

Solid State

Types of Solids:

Based on the nature of the order that is present in the arrangement of their constituent particles solids can be divided into two types;

  • Amorphous solids behave the same as super cool liquids due to the arrangement of constituent particles in short-range order. They are isotropic and have a broad melting point (range is about greater than 5°C).
  • Crystalline solids have a fixed shape and the constituent particles are arranged in a long-range order.