Question

Which kind of defects are introduced by doping?

• A. Dislocation defect
• B. Schottky defect
• C. Electronic defects
• D. Frenkel defect

Answer 1

The correct option is C Electronic defects

$\text{Analyzing the options}$

Option (A):

Dislocation defect is a linear irregularity within a crystal structure that contains an abrupt change in the arrangement of atoms.


Option (B):

Schottky defect in ionic crystals arises when equal number of cations and anions are missing from the normal site of lattice, resulting in equal number of cation and anion vacancies.

Option (C):

Frenkel defect in ionic crystals arises when a cation is missing from the normal lattice position and occupies an interstitial site.

Option (D):

Doping introduces electronic defects. The electronic defect occurs due to the addition of electron-rich or electron-deficient impurity to a perfect crystal. There are $2$ types of dopants: $n-$type and $p-$type.

The $n-$ type semiconductor is formed when, silicon is doped with electron-rich impurities. As group $14$ element $Si$ has $4$ valence electrons, therefore, to get an extra electron carrier for the semiconductor it must be doped with elements of valency $5$

i.e., group $15$ elements such as $P$ or $As$.


The $p-$ type semiconductor is formed when silicon is doped with electron-deficient impurities. As group $14$ element, $Si$ has $4$ valence electrons, therefore, to get a deficiency of electron for the semiconductor it must be doped with elements of valency $3$

i.e., group $13$ elements such as $B$ or $In$.