Silicon Semiconductor: Properties, Applications, and Advantages

What is a silicon semiconductor?

A silicon semiconductor is elemental silicon whose electrical conductivity lies between that of a conductor and an insulator. Crystalline silicon is an indirect-band-gap semiconductor with a band gap of about 1.12 eV at room temperature. Manufacturers control its carrier concentration and conductivity through doping, electric fields and light, which makes silicon useful in integrated circuits, transistors, power devices and photovoltaic cells.

Why is silicon used as a semiconductor?

Silicon is widely used as a semiconductor because its material properties work well with mature, repeatable manufacturing processes:

• It is the second most abundant element in Earth’s crust after oxygen. The raw material is abundant, although producing semiconductor-grade silicon still requires extensive purification.
• It has a high melting point of about 1414 °C, and mature silicon devices can control substantial currents. A device’s safe junction temperature and current are set by its design, package and data-sheet ratings, not by one universal 150 °C limit.
• Its band gap is about 1.12 eV at room temperature. Thermal energy or absorbed light can create electron-hole pairs, while doping provides controlled carrier concentrations for practical devices.
• Controlled oxidation can grow a silicon dioxide (SiO2) layer on the surface. This electrically insulating layer and its interface with silicon are central to metal-oxide-semiconductor fabrication, although oxide quality and interface defects must be carefully controlled.
• It can be doped with different impurities to create n-type or p-type semiconductors, which are used to form pn junctions and other devices.

How does silicon semiconductor work?

Each silicon atom has four valence electrons that form covalent bonds with four neighboring atoms in a diamond-cubic crystal structure. At absolute zero (0 K), an ideal silicon crystal has no thermally generated free charge carriers and behaves as an insulator.

As temperature rises, some electrons gain enough energy to enter the conduction band and leave holes in the valence band. Electrons and holes move under an electric field and carry current. Temperature changes both the carrier concentration and carrier mobility, so the temperature coefficient of resistance depends on the silicon’s doping, temperature range and device structure.

Silicon’s conductivity can be controlled by adding small, measured amounts of dopants. If an atom with five valence electrons, such as phosphorus, replaces a silicon atom, it donates an extra electron and creates an n-type semiconductor in which electrons are the majority carriers. If an atom such as boron contributes only three electrons to bonding, it leaves an empty state in the valence band. These mobile holes become the majority carriers in p-type silicon.

Joining n-type and p-type regions creates a pn junction whose electrical behaviour can be controlled by applied voltage. These junctions form diodes, which conduct much more readily in one direction, and help form transistors that switch or amplify signals. Integrated circuits combine many such devices and connections on one chip.

What are some applications of silicon semiconductors?

Silicon semiconductors serve several major roles in electronics:

• Power devices: Silicon is used in diodes, thyristors, IGBTs, MOSFETs and other mature devices that control a wide range of voltages and currents in converters, drives and control systems. Silicon carbide and gallium nitride devices can offer better performance at some high-voltage, high-temperature or high-frequency operating points.
• Integrated circuits: Silicon fabrication can place millions or billions of transistors and other components on one chip. These chips provide memory, logic, processing, communication and sensing functions.
• Photovoltaic cells: Silicon converts absorbed sunlight into electrical energy in solar cells. Crystalline silicon dominates the commercial photovoltaic market, but it is not the highest-efficiency technology in every laboratory or multi-junction comparison.
• Transistors: Silicon is used to make bipolar junction transistors (BJTs) and metal-oxide-semiconductor field-effect transistors (MOSFETs). These basic electronic building blocks switch or amplify signals in analogue, digital and power circuits.

What are some advantages of silicon semiconductors?

Silicon remains useful because its supply chain, device designs and fabrication methods are highly developed:

• It supports mature fabrication techniques, including lithography, etching, doping, oxidation, deposition and bonding.
• Controlled crystal growth, purification and processing can produce high-quality material with low defect and unintended impurity concentrations.
• Its large production base and economies of scale support broad availability and competitive device costs.
• Established silicon device families cover logic, memory, sensing, analogue circuits, power conversion and photovoltaic energy conversion.

Conclusion

Silicon is an indirect-band-gap semiconductor whose electrical behaviour can be controlled through doping and device structure. Its crustal abundance, controllable oxide, mature manufacturing base and broad device range explain its central role in electronics. Actual current, voltage, temperature and efficiency limits depend on the finished device, and other semiconductor materials can perform better in specialised operating conditions.