Semiconductor Series — 0001. What Are Semiconductors?

This is a series of short posts (5–10 minutes each post) about semiconductors to sparse the knowledge on this fast-growing industry.

Introduction to Semiconductors

Semiconductors are the essential building blocks of modern electronics because they form the basis of devices like transistors, diodes, and integrated circuits (ICs), the key components in almost all electronic devices. They are materials with electrical properties categorized as conductors and insulators (to be discussed in future posts). Their unique ability to control the flow of electrical current, thanks to their conductivity properties (which can be altered by doping or external voltage), makes them versatile. This allows the creation of switches, amplifiers, and logic gates, which are foundational for digital circuits in computers, smartphones, and countless other technologies. Semiconductors have revolutionized technology, making it possible to miniaturize and enhance the performance of electronic systems. Today, they are found in almost every piece of technology.

Unlike conductors that allow current to flow freely, or insulators that prevent current flow, semiconductors can either conduct or resist electricity based on certain conditions (to be discussed in future posts). This tunable property is what makes semiconductors so essential in electronic components like transistors and diodes, which can act as switches or amplifiers in circuits.

Historical Context

Semiconductors began replacing vacuum tubes in the mid-20th century, marking a major leap in electronic technology. A pivotal moment came in 1947 when Bell Labs invented the first transistor, sparking the development of modern computers and smaller, more efficient electronic devices. This transition from bulky, inefficient vacuum tubes to compact, reliable semiconductor devices revolutionized the electronics industry, leading to today’s digital age.

Early Discoveries

· 1821: Thomas Johann Seebeck discovered the thermoelectric effect, which demonstrated how the application of heat could induce an electric current in certain materials.

· 1833: Michael Faraday observed that the electrical resistance of silver sulfide decreases as the temperature increases, unlike metals whose resistance increases with temperature. This was an early clue that materials like silver sulfide had unique properties that didn’t fit into the typical categories of conductors or insulators.

The Birth of Solid-State Physics

· 1874: Karl Ferdinand Braun observed the unidirectional behaviour of crystals. They could allow current to flow in one direction, marking the discovery of rectification, which is the fundamental principle of a diode.

· 1901: American inventor Greenleaf Whittier Pickard developed the first crystal detector, a primitive semiconductor device used in early radio receivers.

From Vacuum Tubes to Transistors

· 1947: The transistor was the first solid-state device capable of amplifying electrical signals and replacing the bulky and fragile vacuum tubes used in electronics. This invention, by John Bardeen, Walter Brattain, and William Shockley at Bell Labs, laid the foundation for modern electronics and earned the Nobel Prize in Physics in 1956.

· 1950s: The development of semiconductors accelerated in this epoch. Germanium was initially the primary material used in transistors, but silicon soon replaced it due to its superior properties.

The Rise of Silicon and the Integrated Circuit

· 1958: Jack Kilby at Texas Instruments and Robert Noyce at Fairchild Semiconductor independently developed the IC. This invention allowed multiple transistors and electronic components to be placed on a single chip, revolutionizing electronics by drastically reducing size, power consumption, and cost while increasing reliability and functionality. We are going to discuss how this was achieved in a future post.

The Birth of the Semiconductor Industry

· 1960s: Silicon rapidly became the dominant material for semiconductors due to its availability and the development of the silicon planar process, which allowed for the mass production of ICs.

· 1968: Robert Noyce and Gordon Moore left Fairchild Semiconductor to form Intel, one of the companies that would drive the semiconductor revolution.

Moore’s Law and the Digital Revolution

· 1971: Intel introduced the first microprocessor, the Intel 4004, which was a milestone in computing history. The ability to fit an entire CPU on a chip marked the beginning of modern computing.

· 1970s–1980s: Moore’s Law — Gordon Moore’s observation that the number of transistors on a chip doubles roughly every two years — became the driving force behind exponential increases in processing power, leading to the digital revolution.

Modern Semiconductor Era

· 1990s–2000s: Semiconductors powered the rise of personal computers, mobile phones, and the internet.

· Present Day: Semiconductors are found in nearly every aspect of modern life. They power smartphones, tablets, computers, cars, appliances, medical devices, and even advanced technologies like AI and IoT. The industry’s focus has shifted towards shrinking the size of transistors, improving performance, and reducing power consumption.

Why are Semiconductors Important?

Semiconductors are crucial because are the foundation for key electronic components like transistors, microchips, and ICs. These components enable the functioning of a vast array of devices that we rely on daily, including smartphones, computers, household appliances, solar panels, and even medical devices. Without semiconductors, the high-speed processing and miniaturization seen in modern electronics would not be possible.

Basic Properties of Semiconductors

One of the defining characteristics of semiconductors is their adjustable conductivity, which can be fine-tuned by adding impurities — a process known as doping. This versatility allows semiconductors to be customized for specific electronic functions.

There are two types of semiconductors:

· Intrinsic Semiconductors: Pure materials without any added impurities, having moderate conductivity.

· Extrinsic Semiconductors: Doped semiconductors, where impurities are introduced to enhance their electrical properties.

Common Semiconductor Materials

Some of the most commonly used semiconductor materials include:

· Silicon: The most widely used material in the semiconductor industry due to its abundance, low cost, and favourable electrical properties.

· Germanium: One of the earliest semiconductor materials, though less common today.

· Gallium Arsenide: Used in high-speed electronics and optoelectronic devices due to its superior performance in certain applications.

Silicon dominates the industry because of its cost-effectiveness and its properties that allow for the efficient fabrication of large-scale integrated circuits.

Basic Structure of Semiconductor Devices

Semiconductors are the building blocks of devices like diodes and transistors. A diode allows current to flow in only one direction, while a transistor amplifies signals or switches electrical currents on and off. These devices form the core of modern electronic circuits, and in future posts, we’ll explore how they work in more detail.

Reference

[1] R. F. Pierret, Semiconductor device fundamentals. New Delhi (Indai): Pearson/Education, 2008.

[2] Massimo Rudan, Physics Of Semiconductor Devices. S.L.: Springer International Pu, 2018.

[3] N. H. E. Weste and David Money Harris, CMOS VLSI design: a circuits and systems perspective. Noida: Pearson, 2015.

[4] J. M. Rabaey, Digital Integrated Circuits. Pearson, 2016.