What Is a Semiconductor?

What is a semiconductor?

A semiconductor is a material with electrical conductivity between that of a conductor and an insulator. It is used in the manufacture of electronic devices such as transistors, diodes, and integrated circuits. Semiconductors can be manipulated to control the flow of electrical current, making them essential for modern electronics and computing. Examples of semiconductors include silicon and germanium.

 

Properties of Semiconductors

Semiconductors have several unique properties that make them useful in electronics and computing:

• Conductivity: Semiconductors have electrical conductivity intermediate between that of conductors and insulators. This property can be manipulated by adding impurities (doping) to control the flow of electrical current.
• Bandgap: Semiconductors have a bandgap, an energy gap between the valence and conduction bands, which determines its electrical behavior.
• Temperature sensitivity: The electrical conductivity of a semiconductor is sensitive to temperature, making them useful in temperature sensors.
• Photoconductivity: Semiconductors show an increase in electrical conductivity when exposed to light, making them useful in photovoltaic cells.
• Heterojunction: When two different semiconductors are brought into contact, they form a heterojunction, which has unique electrical properties that are useful in devices such as solar cells and LEDs.

High resistance to thermal and electrical shock: Semiconductors are relatively resistant to thermal and electrical shock, making them suitable for use in harsh environments.

 

Types of Semiconductors

There are two main types of semiconductors: intrinsic and extrinsic. Intrinsic semiconductors are pure materials, such as silicon and germanium, that have only a few free electrons. Extrinsic semiconductors have impurities added, called doping, to increase the number of free electrons. The two most common types of extrinsic semiconductors are n-type and p-type.

N-Type Semiconductors

An n-type semiconductor is a material in which the majority of charge carriers are electrons with a negative charge. This is achieved by adding impurities called "dopants" to the material, which provide extra electrons for electrical conduction. Examples of n-type dopants include phosphorus, arsenic, and antimony. N-type semiconductors are used in many electronic devices such as diodes, transistors, and solar cells.

P-Type Semiconductors

A p-type semiconductor is a material in which the majority of charge carriers are "holes," or vacancies in the crystal lattice where electrons are missing. These holes have a positive charge and can conduct electricity. P-type semiconductors are formed by adding impurities such as boron, aluminum, or gallium to the material, which have fewer electrons than the semiconductor atoms, creating the holes. P-type semiconductors are used in many electronic devices such as diodes, transistors, and solar cells, and play an important role in creating the p-n junctions that are essential for many electronic devices to function properly.

 

History of Semiconductor

The history of semiconductors dates back to the late 19th century, when scientists first discovered that certain materials, such as germanium and silicon, had electrical properties that could be controlled and manipulated. In the early 20th century, researchers developed the first vacuum tube devices, which relied on the flow of electrons through a vacuum to perform tasks such as amplification and rectification. However, vacuum tubes were large, expensive, and unreliable, and their limitations led to the development of the first semiconductor devices in the mid-1940s.

The invention of the transistor in 1947 by Bell Labs marked a major turning point in the history of semiconductors. The transistor was a much smaller, more reliable, and more efficient alternative to vacuum tubes, and it paved the way for the development of the first commercial computers in the 1950s. In the decades that followed, the semiconductor industry exploded, driven by rapid advances in technology and the growing demand for electronic devices.

One of the most significant milestones in the history of semiconductors was the invention of the microprocessor in the 1970s. This tiny integrated circuit, which combined multiple transistors on a single chip, paved the way for the development of the personal computer and the rise of the tech industry in Silicon Valley. Today, semiconductors play a critical role in virtually all modern electronic devices, from smartphones and laptops to medical devices and self-driving cars.

The history of semiconductors is a story of innovation and technological advancement, driven by the relentless pursuit of smaller, faster, and more powerful devices. From its humble beginnings as a research field to its current status as a cornerstone of modern society, the history of semiconductors continues to evolve, shaping our world and changing the way we live, work, and communicate.

 

Semiconductor Devices

Semiconductors are used in a variety of electronic devices, including transistors, diodes, and integrated circuits. Transistors are used as amplifiers or switches in electronic circuits. Diodes are used to convert AC current to DC current and to protect circuits from voltage spikes. Integrated circuits are used to control the flow of electrical current in complex electronic systems.

 

Manufacturing of Semiconductors

The manufacturing of semiconductors involves a complex process that includes multiple steps such as wafer fabrication, assembly, and testing.

• Wafer fabrication: The process starts with a silicon wafer, which is a thin disk of pure silicon. Impurities are introduced into the wafer to create an excess or deficiency of electrons, creating "p" and "n" type semiconductors. The wafer is then patterned using photolithography, where a photosensitive material is applied, and a mask is used to transfer a pattern onto the wafer. The patterned wafer is then etched to create the desired structures.
• Assembly: The individual semiconductor devices are then assembled onto a wafer. This is done by adding various layers, including metal interconnects, onto the surface of the wafer.
• Testing: Finally, the wafers are diced into individual chips, which are then tested for functionality and performance. Good chips are packaged and sold, while the defective ones are discarded.

The entire process of semiconductor manufacturing is done in a cleanroom environment to minimize contamination, and specialized equipment is used to carry out each step. The manufacturing process is constantly being improved and optimized to increase production efficiency and reduce costs.

 

Advantages of Semiconductors

Semiconductors have several advantages over other materials, including:

• High resistance to heat and electrical conductivity
• Low cost and easy to manufacture
• Easy to integrate into devices and systems
• Versatile applications in electronics and computing
• Ability to control the flow of electrical current
• Durable and able to operate over a wide range of temperatures
• High power efficiency and low power consumption.

 

Disadvantages of Semiconductors

Semiconductors also have some disadvantages, including:

• Vulnerability to damage from excess heat or electrical current
• Limited operating temperature range
• Performance degradation over time
• Complex fabrication processes requiring specialized equipment
• Limited charge storage capacity in comparison to other materials like batteries.
• Costly raw materials, leading to high costs for certain applications.

 

Conclusion

Semiconductors are essential components in electronic devices, including transistors, diodes, and integrated circuits. Semiconductors have unique electrical properties that make them useful in electronics. Semiconductors are manufactured using a combination of mechanical and chemical processes, and are typically made from silicon due to its abundance and electrical properties. Although there are some disadvantages to using semiconductors, such as their cost and sensitivity to temperature, their advantages, such as reliability, durability, energy efficiency, and compactness, make them an important part of modern electronics. In conclusion, semiconductors play a crucial role in the functioning of many electronic devices and will likely continue to be an important part of electronics in the future.