When the electrical conductivity of a semiconductor is due to the breaking of its covalent bonds, then the semiconductor is said to be :

CONCEPT:

• The material which is not a good conductor or a good insulator is called the semiconductor.
• For example Silicon, Germanium, etc.

Two types of semiconductor:

1. Intrinsic semiconductors: It is an undoped semiconductor or pure semiconductor without adding any impurity
2. Non-intrinsic or extrinsic semiconductor: It is a semiconductor that is doped with a specific impurity that can deeply modify its electrical properties, making it suitable for electronic applications (diodes, transistors, etc.)

• Depending upon the impurity added non-intrinsic semiconductors can be classified into P-type and N-type of semiconductors depending on whether the semiconductor is rich in holes or electrons.

EXPLANATION:

• ​An intrinsic semiconductor is made up of only a single type of element.
• Germanium (Ge) and Silicon (Si) are the most common type of intrinsic semiconductor.
• When the temperature rises, due to collisions, some covalent bonds break and few electrons are unbounded and become free to move through the lattice, thus creating an absence in its original position (hole).​ Hence, option 3 is correct.