The transistor turns sixty

As described in last month’s Pioneers’ Page, an early method for amplifying electric signals to produce sound was the carbon microphone. By the start of the 20th century, thermionic valves (or vacuum tubes) were being used for amplification in many types of equipment, from telephone systems to radio sets.

Some readers might remember how, in the first half of the last century, radios containing valves took a while to warm up before sound could be heard. The glow of these sets may have created a cozy atmosphere, but they were hardly portable. And vacuum tubes not only gave off heat: they were also bulky and fragile. It was not until the 1940s that a breakthrough came. It made possible today’s digital world.

Semiconductor research

Some materials can both conduct electricity and resist its flow. Called semiconductors, they include the elements germanium and silicon. Under the influence of electrical fields they can either amplify a signal or close a circuit. The use of crystals to receive radio waves goes back to the late 19th century, and research into using such "solid-state" materials was carried out in the 1920s and 1930s. However, there was incomplete understanding of how these worked.

In 1945, a team of physicists at Bell Telephone Laboratories, in New Jersey, United States, was asked to investigate the topic. The team was led by William Shockley, with John Bardeen and Walter Brattain. After two years, Bardeen and Brattain discovered how to make an amplifying circuit using germanium, which they showed to Bell executives in December 1947. It later became known as the transistor — and 2007 sees the 60th birthday of one of the most important pieces of technology ever invented.

How it worked

In 1956, Bardeen, Brattain and Shockley shared the Nobel Prize for physics "for their researches on semiconductors and their discovery of the transistor effect." It works because pure germanium or silicon are good insulators. But if contaminated, or "doped", with other substances, they produce either a surplus of negatively charged electrons, or steal electrons from the semiconductor to produce "holes" that can carry a positive charge. If you place a negative electrode against a semiconductor with negative carriers, the current is blocked. The insulating property can be removed by electrically injecting positive "holes" that attract the negative carriers.

The world’s first transistor was a "point-contact" type. It was overtaken by the "junction transistor" invented by Shockley in 1948, which comprised a "sandwich" of three regions of germanium. This blocked the flow of electricity both ways until a small current was applied to the middle region to let a much larger current flow through the whole device. Thus, the transistor could act as either a switch or an amplifier. The new technology could produce controllable conductivity — at low cost, little power, small size and good durability.

A mass-market, mobile device

In 1954, the Regency TR-1 transistor radio was launched as the world’s first mass-produced, mobile communication device Steven Reyer

Hearing aids were the first application for transistors. Then, in 1953, the first ever radio using a transistor was demonstrated by the German company Intermetall at the Düsseldorf Radio Fair. In fact, it used four "transistrons" developed independently by German physicists Herbert F. Mataré and Heinrich Welker.

In the United States the following year, two companies, Texas Instruments and Industrial Development Engineering Associates, cooperated to make the "Regency TR-1" that was advertised as "the world’s first pocket radio".

This portability began a revolution. No longer was a radio a piece of living-room furniture; now, it was a personal accessory. The TR-1 was small but expensive (USD 49.95, or about USD 400 today), and it was soon overtaken by transistor radios manufactured in Japan. Nevertheless, with parts that were specially designed to fit its size, the TR-1 had heralded the development of miniature electronic components.

Transistor technology had other, far-reaching effects. An expert on the first transistor radios, Dr Steven Reyer, Professor in the Electrical Engineering and Computer Science Department at the Milwaukee School of Engineering, United States, has described the TR-1 as "in some ways, really ushering in the beginnings of the information age. That is, many of the electronic devices that we have today are based on the transistor in one form or another — either individual transistors, as appeared in this radio, or, in the case of personal computers, many millions of transistors embedded in integrated circuits".

Heading for Silicon Valley

Using transistors based on silicon, those integrated circuits (or microchips) revolutionized the world of computing. They were spearheaded by William Shockley. After leaving Bell Labs in 1955, he directed a semiconductor research and manufacturing company at Mountain View, California, United States. Colleagues went on to form Fairchild Semiconductor Corporation, which developed some of the first integrated circuits at a location that became part of "Silicon Valley".

Shockley later became a professor at nearby Stanford University. A meeting was held there in 2002 to remember those days. It confirmed (and to answer the question posed in last month’s Pioneers’ Page) that "Shockley is the man who brought silicon to Silicon Valley."