Question

Silicon doped with electron rich impurity forms:

• A. p-type semiconductor
• B. n-type semiconductor
• C. Intrinsic semiconductor
• D. Insulator

Answer 1

The correct option is B

n-type semiconductor

The explanation for the correct option:

Option B

n-type semiconductor:

• An n-type semiconductor is created by adding pentavalent impurities like phosphorus$\left(\mathrm{P}\right)$, arsenic$\left(\mathrm{As}\right)$, antimony$\left(\mathrm{Sb}\right)$, or bismuth$\left(\mathrm{Bi}\right)$.
• A pentavalent impurity is called a donor because it is ready to give a free electron to a semiconductor and silicon is a semiconductor.
• A pentavalent impurity is an electron-rich impurity.

The explanation for the incorrect option:

Option A

p-type semiconductor :

• In a p-type semiconductor, trivalent impurity from the III group elements is added as the impurity.
• Trivalent impurities like Aluminium($\mathrm{Al}$) Indium($\mathrm{In}$), and Gallium($\mathrm{Ga}$) are added to the intrinsic semiconductor.
• The trivalent impurities are added to provide extra holes known as the acceptor atom.
• The majority of carriers in a p-type semiconductor are holes.

Option C

Intrinsic semiconductor:

• Semiconductors that are chemically pure, in other words, free from impurities are termed intrinsic semiconductors.
• The number of holes and electrons is therefore determined by the properties of the material itself instead of the impurities.
• In intrinsic semiconductors, the number of excited electrons is equal to the number of holes, n = p.
• They are also termed undoped semiconductors or i-type semiconductors.

Option D

Insulator:

• Insulators are bad conductors of heat and electricity.
• An electrical insulator is a material in which electric current does not flow freely.
• The atoms of the insulator have tightly bound electrons which cannot readily move.
• For example, wood, plastic, etc.

Therefore, option B is correct.