What is a silicon semiconductor?
A silicon semiconductor is defined as a material that has an electrical conductivity value between that of a conductor and an insulator, and whose conductivity can be altered by introducing impurities or applying external fields or light. Silicon is the most widely used semiconductor material in modern electronics, especially in power devices, integrated circuits, photovoltaic cells, and transistors.
Why is silicon used as a semiconductor?
Silicon is used as a semiconductor because it has several advantages over other materials, such as:
- It is the second most abundant element on earth after oxygen, making it readily available and inexpensive.
- It has a high melting point (1414 °C) and can withstand high temperatures (up to 150 °C) and currents, making it suitable for power applications.
- It has a relatively low band gap energy of 1.1 eV, which means it requires less energy to free the valence electrons in the crystal structure and create charge carriers.
- It can form a thin layer of silicon dioxide (SiO2) on its surface when exposed to air or water, which acts as an excellent insulator and protects the underlying silicon from contamination and corrosion.
- It can be doped with different impurities to create n-type or p-type semiconductors, which are essential for forming pn junctions and other devices.
How does silicon semiconductor work?
Silicon has four valence electrons in its outermost shell and forms a covalent bond with four neighboring atoms in a diamond-like crystal lattice. At absolute zero temperature (0 K), silicon behaves as an insulator because all the electrons are tightly bound to the atoms, and there are no free charge carriers.
However, as the temperature increases, some of the electrons gain enough thermal energy to break free from the covalent bonds and become conduction electrons. These electrons can move under the influence of an applied electric field and contribute to the electrical conductivity of silicon. This means that silicon has a negative temperature coefficient of resistance, unlike metals which have a positive one.
The conductivity of silicon can also be increased by doping it with impurities that have either more or fewer valence electrons than silicon. For example, if an impurity atom with five valence electrons (such as phosphorus) replaces a silicon atom in the lattice, it will donate one extra electron to the conduction band. This creates an n-type semiconductor, which has more free electrons than holes (empty spaces where electrons can move). On the other hand, if an impurity atom with three valence electrons (such as boron) replaces a silicon atom in the lattice, it will accept one electron from the valence band. This creates a p-type semiconductor, which has more holes than electrons.
By combining n-type and p-type semiconductors in various ways, different devices can be created that have useful properties, such as passing current more easily in one direction than the other (diodes), amplifying or switching signals (transistors), or integrating multiple functions on a single chip (integrated circuits).
What are some applications of silicon semiconductors?
Silicon semiconductor has many applications in various fields of electronics, such as:
- Power devices: Silicon is used to make diodes, thyristors, IGBTs, MOSFETs, and other devices that can handle high voltages and currents in power conversion, transmission, distribution, and control systems.
- Integrated circuits: Silicon is used to fabricate microchips that integrate millions or billions of transistors and other components on a single chip. These chips are used for various purposes, such as memory, logic, processing, communication, and sensing.
- Photovoltaic cells: Silicon is used to convert sunlight into electricity in solar cells. Silicon-based solar cells are the most common and efficient type of photovoltaic devices.
- Transistors: Silicon is used to make bipolar junction transistors (BJTs) and metal-oxide-semiconductor field-effect transistors (MOSFETs), which are the basic building blocks of modern electronics. These transistors can amplify or switch electrical signals in various circuits and systems.
What are some advantages of silicon semiconductors?
Silicon semiconductor has many advantages over other semiconductor materials, such as:
- It is compatible with various fabrication techniques, such as lithography, etching, doping, oxidation, deposition, and bonding.
- It has a high-quality crystalline structure and purity, which reduces defects and improves performance.
- It has a large market share and economy of scale, which lowers the cost and increases the availability of silicon-based devices.
- It has a wide range of applications and functions, which makes it versatile and adaptable to different needs and demands.
Silicon semiconductor is a material that has intermediate electrical conductivity and can be modified by doping or external stimuli. It is the most widely used semiconductor material in modern electronics because of its availability, durability, conductivity, compatibility, quality, cost-effectiveness, and versatility. Silicon semiconductor is used for making power devices, integrated circuits, photovoltaic cells, transistors, and other devices that have various applications in communication, computing, control, sensing, and energy conversion systems.