Bell Labs’ John Bardeen, Walter Brattain, and William Shockley won the 1956 Nobel Prize in Physics for their 1947 invention of a small semiconductor device called the transistor that would change the world.

Today, there are trillions of transistors on Earth, in every place where an electronic gadget can be found. There are several billion more in space, in satellites and spacecraft. The transistor is the workhorse of electronic technology, the device that heralded the start of the digital age. In its wake, entire industries based on semiconductors were created. Indeed, telecommunications as we know it would not have been possible if it were not for the transistor.

The inventors of the transistor had been investigating the properties of semiconductors to see if they could come up with an acceptable substitute for the vacuum tubes and electromechanical relays used in telephone networks of the day. Electromechanical relays had made fully automatic telephone dialing and switching a reality; however, the relays had low speeds. Vacuum tubes were widely used as diodes and triodes in the electronics industry of the time; they, too, had made a lot of things possible in telephony, but they were not very dependable. Under the guidance of Mervin Kelly, the director of Bell Labs research at the time, a group of physicists set about studying semiconductors to see whether they could create a durable alternative that might eventually replace the relay-tube combination in telephone networks. It would prove to be one of the most remarkable technical odysseys in the history of science and technology.

Semiconductors are usually artificial products made from elements such as germanium or silicon, although natural ones like lead sulfide have been known for a long time. Unlike conductors such as metals, which have numerous free electrons to carry an electric current, silicon and germanium have very few charge carriers. However, by adding small amounts of certain contaminants in a process called doping, one can change the number of charge carriers. For example, when a tiny bit of phosphorus is doped into silicon, a good semiconductor is obtained with the electrons donated by the phosphorus acting as charge carriers. Semiconductors obtained in this manner are called n-type semiconductors, since the charge of carriers is negative.

A more remarkable type of semiconductor is formed when a small amount of boron, for example, is doped on silicon. Boron provides a positively charged carrier by stealing an electron from silicon. In place of the electron, a hole is left behind, and this hole can move about within the semiconductor, acting as a carrier of positive charge. These semiconductors are called p-type semiconductors.

A semiconductor may contain both holes and electrons lodged in such proportions that one kind of carrier or the opposite kind will prevail. Much of the technical importance of semiconductors stems from the interplay of holes and electrons.

Bardeen, Brattain, and Shockley had tested various combinations of p-type and n-type semiconductors under different conditions. They were hoping to find a configuration that would allow a thin layer of semiconductor to regulate a large flow of current between two electrodes.

On December 16, 1947, Bardeen, Brattain, and Shockley managed to make the first working transistor, now known as the point-contact transistor. On Christmas Eve, in a demonstration where the physicists spoke into a microphone connected to a circuit with their transistor, the input signal was amplified about eighteen times. A new era in electronics had dawned; the invention of the transistor became the basis for the electronic age.