There are two types of semiconductor : intrinsic semiconductors and extrinsic semiconductors. This article explores the different types of semiconductors—specifically intrinsic and extrinsic—and their properties.
Semiconductors are materials with electrical properties that lie between conductors (which have a high ability to conduct electricity) and insulators (which have a low ability). Their unique ability to control electron flow makes them invaluable in creating electronic devices, including everything from basic diodes to complex integrated circuits.
What is a Semiconductor?
A semiconductor is a material that can conduct electricity under certain conditions, making it neither a good conductor like copper nor a poor conductor like rubber. This ability is primarily due to the energy gap between its valence and conduction bands. Electrons in these materials can move to the conduction band when sufficient energy is applied (through heat or light), making them available for electrical conduction.
Types of Semiconductor
There are two types of semiconductor.
- Intrinsic semiconductor
- Extrinsic Semiconductor
Intrinsic Semiconductors
Intrinsic semiconductors are pure forms of semiconductor materials without any significant impurities. Silicon and germanium are the most common examples, each with a crystalline lattice structure that supports an equal number of free electrons and holes (vacancies that electrons can jump into, facilitating current flow). The properties of intrinsic semiconductors include:
- Temperature Dependence: Their conductivity increases with temperature as more electrons gain enough energy to jump from the valence band to the conduction band.
- Electrical Conductivity: By nature, they have poor conductivity at low temperatures due to the lack of free charge carriers.
Extrinsic Semiconductors
Extrinsic semiconductors are created by introducing impurities into the intrinsic semiconductor, a process known as doping. This doping significantly alters the electrical properties of the semiconductor by introducing free charge carriers. There are two main types of extrinsic semiconductors:
- N-type Semiconductor:
- Doping Material: Phosphorus or arsenic (which have more valence electrons than silicon or germanium).
- Properties: The extra electrons provided by these dopants increase the electron concentration, making them the majority carriers, while holes are minority carriers. This type exhibits greater conductivity than intrinsic semiconductors because the additional electrons enhance the charge flow.
- P-type Semiconductor:
- Doping Material: Boron or gallium (which have fewer valence electrons than silicon or germanium).
- Properties: The lack of valence electrons creates holes, which are the majority carriers in p-type materials. Electrons are the minority carriers here. The conductivity is due to the movement of holes, which effectively transport positive charge.
Properties of Intrinsic Semiconductors
Intrinsic semiconductors have several key properties:
- Controlled Conductivity: Their conductivity can be precisely controlled by manipulating the temperature and exposure to light.
- Energy Efficiency: They are more energy-efficient in their pure state but require precise conditions to function effectively.
Conclusion
The study and application of different types of semiconductors—both intrinsic and extrinsic—have revolutionized the electronics industry. By understanding and manipulating their properties, scientists and engineers can design devices that are increasingly efficient and capable of performing a wide array of functions. Whether in computing, telecommunications, or consumer electronics, semiconductors continue to be at the heart of innovation, driving the development of technology that shapes our world.