Question

To get a n-type semiconductor from silicon, it should be doped with a substance with valence _______.
a. 2
b. 1
c. 3
d. 5

Answer 1

Hint: The n-type semiconductors are those, which are doped with impurity, which will result in an increased number of electrons and hence will have an enhanced conductivity. To solve this question, keep in mind the valency of silicon and consider the valency of the dopant accordingly.

Complete step by step answer:
The n-type semiconductor is a type of material used in electronics. This type of semiconductor is made by adding an impurity to a pure semiconductor such as silicon or germanium. The impurities added in n-type semiconductors are phosphorus, arsenic, antimony, bismuth and some other chemical element.
The impurities used in n-type semiconductors gives a free electron to the semiconductor. Therefore, they are also known as donor impurities. These donor impurities are added in order to make more charge carriers, or electron wires available in the material for conduction. Hence, the doped material will conduct more than the original material.
Therefore, a material with valency greater than the original material is used. Silicon has a valency equal to 4. So, it must be doped by a material with a valency equal to 5.
Therefore, the answer is – option (d) – To get a n-type semiconductor from silicon, it should be doped with a substance with valence 5.

Note: There is another type of semiconductor, which is known as p-type semiconductor. In this type, a trivalent impurity is added to a pure or intrinsic semiconductor (silicon or germanium). Impurities such as Boron (B), Gallium (Ga), Indium (In), Aluminium (Al) etc. are trivalent impurities. They are also called acceptor impurity.