An Introduction to Semiconductors

Semiconductors are essential features of our daily lives. They enable the receival, processing, and storage of data in modern electronics, including computers and smart phones, to bank cash machines and trains. Within emerging technologies, such as artificial intelligence, the Internet of Things, and quantum computing, semiconductors play a significant role.

What Are Semiconductors?

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A semiconductor has a conductivity between an insulator, like glass, and a conductive metal, such as copper. With a dual nature, semiconductors work as conductors when temperature increases and as insulators with decreasing temperature. Unlike conductors, electrons in a semiconductor must obtain energy from an external source, such as ionizing radiation.

There are two kinds of semiconductor: intrinsic and extrinsic. The intrinsic variety are pure with no addition of doping materials or impurities. The extrinsic kind is prepared by doping the material with sufficient amounts of impurity.

Semiconductors are used in the makeup of switching and amplification devices, also known as transistors. Transistors are often considered to be the greatest invention of all time, as this technology is pervasive in everyday life.

Evolution of Semiconductors

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The evolution of semiconductor technology has followed a concept known as Moore’s Law. This law observes that the number of transistors on a microchip double approximately every two years. The increase is consistent with a reduction in the cost of computing hardware.

As a result of this increase, the manufacture of semiconductors has continued to grow as the technology has developed. In 2023, Taiwan SMC makes 54% of the world’s semiconductors, while the biggest consumers of microchips are Apple and Samsung.

The manufacture and development of semiconductors is both an expensive and complex process. US companies invest around one fifth of annual revenue into research and development. Often supply outweighs demand, so researchers are looking for better, more cost effective, and environmentally friendly methods of producing them.

Semiconductor Materials: Silicon and Alternatives

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Silicon is the material of choice in the semiconductor industry because it is widely abundant and relatively inexpensive. The conductive properties of silicon can be enhanced by doping with materials such as phosphorus or boron. Alongside silicon, germanium and gallium arsenide are alternative semiconductor materials.

There are several problems with using silicon:

• It has hit the physical limitation according to Moore’s Law.
• There is an overreliance on the material as a sole resource. Although abundant, silicon is a finite resource.
• The production process is reliant on expensive cooling systems.

Alternative materials can overcome the challenges of silicon. At present, alternative materials can deliver one million times the electrical current compared to silicon. One replacement for silicon is cubic boron arsenide. This material demonstrates superior performance in conducting heat and electricity.

Another contender is diamond, which can be produced in the laboratory. The advantages of diamonds include:

• A wider bandgap (the energy required for electrons and holes to transition from the valence band to the conduction band)
• Higher thermal conductivity
• The ability to be doped to be more or less conductive
• Heat dissipation
• An improved breakdown field enabling diamond diodes to withstand higher voltages

These characteristics have important applications in 5G communications, satellites, and power electronics used in electric vehicles. Although diamonds will be of importance in the coming decades, the cost of this material remains high because prices are set by the jewellery trade.

The Future of Semiconductors

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Semiconductors are essential to technological advances that demand ever smaller, speedier, and lightweight devices. Now they are involved in the emergence of quantum computing.

There are two major applications for semiconductors in quantum computing: qubits and quantum computer hardware. Qubits are the basic building blocks of quantum processors. They operate on the quantum concepts of superposition (where a particle can be in two different states at once) and entanglement (particles are linked so the fate of one also effects the other). These states can be set by controlling microwave or radio frequency pulses sent to qubits via semiconductor-based wiring.

In the future, quantum computers will outstrip classical computers by far in terms of speed, problem solving and energy efficiency.