Intrinsic vs. Extrinsic Semiconductors

Semiconductors are materials with electrical conductivity between that of conductors and insulators. They are the foundation of modern electronics. Semiconductors can be classified into two types: intrinsic and extrinsic.

Intrinsic Semiconductors

Intrinsic semiconductors are pure semiconductor materials. Their electrical properties are determined by the material's properties, There are two types of Materials used for Intrinsic semiconductors

Examples

Silicon (Si)
Germanium (Ge)

Properties

They act as perfect insulators at absolute zero but as the temperature increases, their conductivity improves.
Thermal energy generates electron-hole pairs At room temperature which are responsible for electrical conduction.
The energy band gap is small.
They are Purely composed of semiconductor material without impurities.

Advantages

Intrinsic semiconductors are pure.
Their electrical properties are well predictable based on temperature and material characteristics alone.
They can be useful in high-precision applications.
This is Ideal for fundamental research and in applications where the impact of dopants must be avoided.

Disadvantages

At room temperature, intrinsic semiconductors have lower electrical conductivity than extrinsic semiconductors.
Their conductivity increases with temperature due to the generation of electron-hole pairs.
Doped semiconductors (extrinsic) are preferred due to their higher conductivity and controlled carrier concentrations.

Applications

They are used in devices where the effects of impurities must be minimized, such as in certain types of sensors.
They are used in some photodetectors and light sensors.
it is used for research purposes.
Some high-purity solar cells use intrinsic semiconductors to ensure that their electrical performance is not influenced by dopants.

Extrinsic Semiconductors

Extrinsic semiconductors are semiconductors that have been intentionally doped with specific impurities to modify their electrical properties. This doping process introduces additional charge carriers into the material. This enhances its electrical conductivity compared to intrinsic semiconductors.

Doped silicon (Si) or germanium (Ge) are common, with elements like phosphorus (P) or boron (B) used as dopants.

Types

N-Type Semiconductors
P-Type Semiconductors

N-type Semiconductor:

N-type semiconductors are doped with elements that have 5 valence electrons (like phosphorus, arsenic, or antimony). These impurities donate extra electrons, which become the majority charge carriers.

The extra electrons improve the semiconductor's conductivity. Electrons are the majority charge carriers, while holes (positive vacancies) are the minority charge carriers.

P-type Semiconductor

P-type semiconductors are doped with elements that have 3 valence electrons (like boron, aluminium, or gallium). The doping creates "holes" where electrons are missing, which act as positive charge carriers.

The movement of holes improves the conductivity. Holes are the majority charge carriers, while electrons are the minority charge carriers.

Advantages

Doping increases the number of charge carriers, significantly improving electrical conductivity compared to intrinsic semiconductors.
Doping allows precise control over the semiconductor's electrical characteristics.
Extrinsic semiconductors provide improved performance for electronic devices, allowing for faster switching speeds and lower power consumption.

Disadvantages

Excessive doping can lead to unwanted effects, such as increased scattering of charge carriers, which can degrade performance.
While less sensitive to temperature changes than intrinsic semiconductors, the performance of extrinsic semiconductors can still be affected by temperature variations.
Prolonged exposure to high temperatures or radiation can cause degradation of the doped semiconductor material.
The doping process can introduce additional complexity and cost in semiconductor fabrication.

Applications

They are used in digital and analogue circuits for amplification and switching applications.
They Utilize extrinsic semiconductors to control current flow.
They Convert AC to DC and regulate current flow in various electronic devices.
They Provide voltage regulation and reference.
They Use extrinsic semiconductors to perform complex computational and storage functions.
p-type Utilize extrinsic semiconductors to convert sunlight into electrical energy with improved efficiency.
They Employ extrinsic semiconductors to emit light in various colours and intensities.

Intrinsic vs Extrinsic Semiconductor

Intrinsic and extrinsic semiconductors are fundamental to the electronics industry, with extrinsic semiconductors being crucial for creating the wide range of devices we rely on today.

Conclusion

Both intrinsic and extrinsic semiconductors play vital roles in modern electronics. They offer enhanced conductivity and are crucial for creating high-performance devices such as diodes, transistors, and integrated circuits.

Frequently Asked Questions – FAQs

Which are more conductive, intrinsic or extrinsic semiconductors?

Extrinsic semiconductors are generally more conductive than intrinsic semiconductors because the added impurities increase the number of charge carriers available for conduction.

Why are extrinsic semiconductors more commonly used in electronic devices?

Extrinsic semiconductors are preferred because their electrical properties can be precisely controlled through doping.

Can the type of extrinsic semiconductor be changed?

Yes, by altering the type of dopant, an N-type semiconductor can be turned into a P-type and vice versa.

How does temperature affect intrinsic semiconductors?

In intrinsic semiconductors, as temperature increases, more electrons gain enough energy to jump from the valence band to the conduction band, increasing conductivity.