Question

Assertion : An n-type semiconductor has a large number of electrons but still it is electrically neutral.
Reason : An n-type semiconductor is obtained by doping an intrinsic semiconductor with a pentavalent impurity.

• A. If both assertion and reason are true and reason is the correct explanation of assertion
• B. If both assertion and reason are true but reason is not the correct explanation of assertion
• C. If assertion is true but reason is false
• D. If both assertion and reason are false

Answer 1

Answer: (B)

A n-type semiconductor is formed by doping pure germanium or silicon crystal with suitable impurity atoms of valency five. As the impurity atoms take the position of Ge atom in germanium crystal, its four electrons form covalent bonds by sharing electrons with the neighbouring four atoms of germanium whereas the fifth electron is left free. Since the atom on the whole is electrically neutral, the n-type semiconductor is also neutral.