A guide to semiconductors- and their role in shaping the future of modern technology

Our useful guide to semiconductors explores their integral role in modern technologies, and how they are paving the way for future innovation.

Adam Jeffery Product Manager for Board Mount Sensors and Semiconductors at Distrelec

Adam has over 8 years’ industry experience and is dedicated to connecting engineers and professionals with the most innovative sensors available on the market. Passionate about technological progress, Adam helps customers enhance their applications by offering high-quality, cutting-edge components.

Semiconductors in modern technology

Semiconductors are at the heart of most technical devices, including electronic games, barcode readers, computers and microprocessors. As an intrinsic component of computerized devices, semiconductors are used widely in the manufacture of diodes, transistors and integrated circuits. Their application has grown exponentially over the last few years as a result of increasingly smaller feature sizes, advances in both semiconductor equipment and semiconducting materials as well as the ability for integrated circuits (ICs) to be mass-produced from a single chip.

What is a semiconductor? 

Semiconductors are not components as such, but are actually materials that can be either pure elements, such as silicon or germanium, or compounds, like gallium arsenide or cadmium selenide. Whilst these materials are neither good conductors nor insulators, they conveniently fall somewhere between the two. Semiconductors (as the name suggests) are capable of conducting electricity, but only when subject to electrical stimulation in a specific direction. This unique ability enables them to act as an electronic switch as they can both conduct and not conduct, providing the 1 or 0 needed in binary computing and digital processing.

Semiconductor devices are small, reliable, cost-effective and power-efficient and, as a result, are suitable for integration into complex microelectronic circuits. As discrete components, they can be used in power devices, light emitters and optical sensors.

There are two types of semiconductors – intrinsic and extrinsic:

The material most commonly used for semiconductor chips and transistors is silicon. So prominent is its use that it gave rise to the term “Silicon Valley”, which is synonymous with many of the most innovative global companies and technological products. Although not naturally a conductor, silicon can be doped so that it behaves like one.

Doping is the process whereby silicon is mixed with an impurity to create an extrinsic semiconductor. Two types of impurities achieve this:

1. N-type doping:

• Small quantities of either phosphorus or arsenic are added to the silicon.
• Phosphorus and arsenic have five outer electrons. When they combine with silicon, the fifth electron has nothing to bond to and so moves around freely.
• N-type silicon is an effective conductor and is so named because electrons have a negative charge.

2. P-type doping:

• Small quantities of either boron or gallium are added to the silicon.
• These elements have just three outer electrons, which create “holes” in the silicon lattice where silicon electrons having nothing to bond to.
• In the absence of electrons, a positive charge results.
• Current is conducted through these holes as the hole accepts an electron from a neighbour, creating a good conductor.

The tiniest amount of either impurities can change the behaviour of silicon from being a good insulator into a viable conductor. This creates a semiconductor.

Diodes

Diodes are created when N-type and P-type silicon are combined. This is the simplest semiconductor device as current flows in one direction but not in the other, enabling it to operate like a switch that can be opened or closed accordingly.

Most devices that use batteries contain a diode that blocks any current from leaving the battery and serves to protect the device if batteries are inserted backwards.

10 types of discrete semiconductors

1. PIN diode

These are often found in high-voltage applications and applications that require fast switching. PIN diodes can be differentiated from other diodes as the semiconductor is sandwiched between a P-type and N-type semiconductor layer.

2. Constant-current diode (also known as a current-limiting diode)

Constant-current diodes are also known as current-limiting diodes. They regulate current rather than voltage and only allow for the current to flow up to a certain value, which the diode maintains.

3. Zener diode

Zener diodes allow current to flow in either a forward or reverse direction. They are frequently used in three ways: to provide a limiting factor on voltage, to protect against excessive voltage or to act as a voltage reference.

4. Rectifier diode 

Rectifier diodes allow current to pass in one direction only. They rectify alternating current by converting it into direct current through the use of rectifier bridges. As they are more robust than standard diodes, they are better able to handle heavier workloads.

5. Transient-voltage-suppression (TVS) diode

TVS diodes are designed to protect sensitive semiconductors from potential damage caused by transient voltages. Attributes include a fast response time, low capacitance and low leakage current making it ideal for electrostatic discharge (ESD) events.

6. Bipolar transistor

Bipolar transistors have carriers that use both negative and positive charges. Common applications for bipolar transistors include switching and amplification. Whilst incorporated into analog circuits extensively, they can also be purchased as discrete units.

7. Darlington transistor

A Darlington transistor is essentially two transistors in one, where the first amplifies current to a specific level and the second amplifies it further. Darlington transistors are often used to minimise space on a board where two transistors might otherwise be used.

8. Junction gate field-effect transistor (JFET)

JFETs are commonly used in switching applications but are also capable of providing resistance that is dependent on voltage. They have source and drain terminals, which can be used to either add resistance to electric current or to cut it off altogether.

9. Metal-oxide-semiconductor field-effect transistor (MOSFET)

MOSFETs are the most commonly used form of transistor due to their use in both analog and digital circuits. They are effectively JFETs with four terminals (body, drain, gate and source terminals), although in practice three of these are typically hooked up when in use. MOSFETs work as a switch by controlling the voltage and current flow between the course and drain.

10. Insulated gate bipolar transistor (IGBT)

IGBTs are a cross between the bipolar transistor and the MOSFET. They benefit from the combination of high switching speeds typical in a MOSFET and the low saturation voltage of a bipolar transistor.

The future of semiconductors

Compound semiconductors, which are made from two or more elements, are the next generation of semiconductors. They are likely to be instrumental in shaping the future of technology and in underpinning the Internet of Things (IoT). Compound semiconductors exceed the capabilities of silicon as they are faster, more efficient and better able to support ultra-high performance technologies. Used extensively in wireless communications, chips made from compounds like gallium arsenide are found in almost every smartphone, enabling high speed and high efficiency communications in both cellular and WiFi networks. Compound semiconductors emit and sense light, which is useful for LEDs, lasers and fibre-optics and is not possible with silicon. This attribute, combined with the greater efficiency of compound semiconductors, will facilitate innovation in a number of areas including 5G, robotics, artificial intelligence (AI), autonomous vehicles and renewable energy.

Developments in quantum computing are also likely to drive semiconductor progress as companies strive to create quantum computers with incredible processing powers. Whilst initial research in this area focused on systems that operate in conditions with a temperature of zero, the inclusion of semiconductors allows for the development of quantum computers that can be used at room temperature. This brings us closer than ever to the commercial realization of quantum computing – a revolutionary revelation for modern society.

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