Question

When a pentavalent impurity is mixed into the semiconductor:

1. The number of electrons becomes more than the number of holes
2. The number of holes becomes more than the number of electrons
3. The number of holes remains equal to the number of electrons
4. None of these

Answer 1

Correct Answer - Option 1 : The number of electrons becomes more than the number of holes

CONCEPT:

Semiconductor: 

• Semiconductors are the materials that have a conductivity between conductors and insulators.
  • Semiconductors are made of compounds such as gallium arsenide or pure elements, such as germanium or silicon.
• There are two types of semiconductor:

1. ​N-type Semiconductor
2. P-type Semiconductor

N-type Semiconductor	P-type Semiconductor
In an n-type semiconductor, pentavalent impurity from the V group is added to the pure semiconductor.	In a p-type semiconductor, trivalent impurity from the III group elements is added as the impurity.
Examples of pentavalent impurities are Arsenic, Antimony, Bismuth, etc.	Trivalent impurities like Aluminium, Indium, and Gallium are added to the intrinsic semiconductor.
The pentavalent impurities provide extra electrons and are termed donor atoms.	The trivalent impurities added provides extra holes known as the acceptor atom.
Electrons are the majority charge carriers in n-type semiconductors.	The majority of charge carriers in a p-type semiconductor are holes.

EXPLANATION:

• In an n-type semiconductor, pentavalent impurity from the V group is added to the pure semiconductor.
• Electrons are the majority charge carriers in the n-type semiconductor.
• So when a pentavalent impurity is mixed into the semiconductor, the number of electrons becomes more than the number of holes.
• Hence, option 1 is correct.