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 pentavelent impurity.
A. If both the assertion and reason are true and reason is a true explantion of the assertion.
B. If both the assertion and reason are true but the reason is not true the correct explantion of the assertion.
C. If the assertion is true but reason false
D. If both the assertion and reason are false.

Answer 1

Correct 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.