Question

 Doping intrinsic Silicon with Arsenic as an impurity
1. Only increases the conductivity of Silicon by increasing the number of free electrons available
2. Produces a semi-conductor in which the charge carriers are predominantly electrons but holes are also present
3. Produces a semi-conductor in which the charge carriers are predominantly holes but free electrons also present
4. Produces a semi-conductor in which the charge carriers contain nearly equal number of electrons and holes 

Answer 1

Correct Answer - Option 1 : Only increases the conductivity of Silicon by increasing the number of free electrons available

Concept:

Doping:

• It is the process of adding impurities into the semiconductor.
• Doping increases carrier concentration and thereby increases the conductivity.
• Pentavalent/Donor Impurities: P, As, Sb, Bi
• Trivalent/Acceptor Impurities: B, Al, Ga, In

Explanation:

• Doping of intrinsic Silicon with Arsenic impurity gives rise to N-type semiconductor as Arsenic is a pentavalent type of impurity.
• In N-type Semiconductor, the current is predominantly dominated by the flow of electrons, hence, no of free electrons increases.

Extrinsic Semiconductor	Intrinsic semiconductor:
The process of adding impurities to a semiconductor gives rise to an extrinsic semiconductor.	An intrinsic semiconductor is also known as a pure semiconductor in which no other material is intentionally doped. Example: Si, Ge
Extrinsic Semiconductor is of two types: 1. N-type Semiconductor: When impurity added is of pentavalent type. Ex P, As. 2. P-type Semiconductor: When impurity added is of trivalent type. Ex B, In.	In an Intrinsic semiconductor, both holes and electrons have equal concentration equal to the intrinsic concentration.
Doping increases carrier concentration and conductivity.