What is Intrinsic semiconductor , Advantage , Disadvantage , Application

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An intrinsic semiconductor is a pure semiconductor material in which no impurity is added. Its electrical properties depend only on the semiconductor material itself.

In intrinsic semiconductors, the number of electrons is equal to the number of holes, and conduction takes place due to thermally generated charge carriers.

Examples: Pure Silicon (Si), Germanium (Ge)

Atomic Structure of an Intrinsic Semiconductor

Intrinsic semiconductors have atoms with four valence electrons.

• Each atom forms covalent bonds with four neighbouring atoms
• These bonds create a stable crystal structure
• At very low temperature (0 K), all electrons are tightly bound

When the temperature increases:

• Some covalent bonds break
• Electrons become free
• Holes are created

Thus, electron-hole pairs are generated.

Energy Band Diagram

Intrinsic semiconductors have three important energy levels:

(a) Valence Band (VB)

• Contains bound electrons
• No conduction takes place here

(b) Conduction Band (CB)

• Contains free electrons
• Responsible for conducting

(c) Forbidden Energy Gap

• Small energy gap (~1 eV for Silicon)
• Electrons can easily jump from VB to CB

Because of this small gap, intrinsic semiconductors can conduct electricity at higher temperatures.

Generation of Charge Carriers

In intrinsic semiconductors, charge carriers are generated by thermal energy.

Process:

1. Heat energy is applied
2. Electrons gain energy
3. Move from the valence band to the conduction band
4. Leave behind a hole

This creates an electron-hole pair

Electron-Hole Pair Concept

When an electron leaves its position:

• The electron becomes a free electron
• The empty space is called a hole

Important Points:

• Electron → Negative charge
• Hole → Positive charge
• Both contribute to the current

In an intrinsic semiconductor:

Number of electrons = Number of holes

Current Conduction in an Intrinsic Semiconductor

Current flows due to both electrons and holes.

(a) Electron Current

• Free electrons move in the conduction band

(b) Hole Current

• Holes move into the valence band
• Actually, electrons move, but it appears like holes move

Total current = Electron current + Hole current

Temperature Effect

Intrinsic semiconductors are temperature sensitive.

Effects:

1. As temperature increases → conductivity increases
2. More electron-hole pairs are generated
3. Resistance decreases

This behaviour is opposite to conductors.

Properties of an Intrinsic Semiconductor

1. Pure material (no impurity)
2. Low conductivity at room temperature
3. An equal number of electrons and holes
4. Conductivity increases with temperature
5. No majority or minority carriers
6. Current depends on temperature

Advantages of Intrinsic Semiconductor

1. Simple structure
2. No impurity required
3. Stable behavior
4. Useful for basic study of semiconductor physics

10. Disadvantages

1. Low conductivity
2. Not suitable for practical electronic devices
3. Cannot control electrical properties easily

11. Applications of Intrinsic Semiconductor

Although intrinsic semiconductors are not widely used directly, they are important for:

1. Understanding semiconductor theory
2. Base material for extrinsic semiconductors
3. Used in research and study