The Invention of the Transistor: History, Impact, and Engineering Marvel

The Invention of the Transistor: History, Impact, and Engineering Marvel

Reach into your pocket and pull out your cell phone. Even if you're rocking the oldest, stripped-down flip phone from 2002, what you have in your hand is a marvel of modern electronics technology, packing billions of tiny switches into just a few cubic centimeters of space. In contrast, the Apollo guidance computer that sent humans to the moon had only 17,000 switches, while the SAGE computer, the size of a three-story building used for North American aerospace defense in the 1950s, had 50,000 switches. This tremendous feat of miniaturization was made possible by advances in integrated circuit manufacturing, in which entire computers, consisting of a few billionths of a meter, are etched onto the surface of tiny silicon chips. But this breakthrough would never have happened if it hadn’t been for a major breakthrough made nearly 80 years ago  a discovery that forever changed the course of technology  and the world. This is the story of the transistor, one of the most important inventions in modern history.

For the first half of the 20th century, electronics design was dominated by a key piece of technology: the vacuum tube. During the thousands of experiments Thomas Edison and his team were trying to create an economically viable incandescent light bulb, a highly revolutionary and far more unique device Edison accidentally invented in parallel with the light bulb was just a slight twist on one of his light bulbs. But unfortunately for Edison, he didn’t realize what he had done in one of his thousands of tests, and how revolutionary it could be if it were slightly improved, and applied in the right way. Because of his failure to realize any of this, nor to perfect it for commercial use, despite his patent for the device, Edison is almost never given credit for his contributions to this world-changing invention. It’s no surprise, as is a theme you’re probably picking up, that he’s the man who ultimately did the thing in its best commercial form, rather than being the first to come up with it, as is usually credited in popular history. Enter English physicist John Ambrose Fleming, an advisor to Edison Electric Light. He would be inspired by Edison’s device to create his revolutionary Fleming valve vacuum tube in the early 20th century.

But going back to Edison’s original device, at one point during his experiments on the light bulb, he and his staff were trying to figure out why carbon from the filament was jumping from the vacuum to the walls of the bulb. Clearly, some current flow was involved. So to try to figure out what was going on here, Edison made a special bulb with a third electrode placed between the legs of the filament, and then connected it to a galvanometer to measure the current. What he found was that if, relative to the filament, the plate was held at a negative potential, there would be no current between the plate and the filament. However, if the plate was at a positive potential, and the filament became sufficiently hot, a large current would flow between the plate and the filament through the gap. The key point here is that electrons can only flow in one direction, from the hot element to the cold element, creating a rudimentary diode.

The Invention of the Transistor: History, Impact, and Engineering Marvel

Edison eventually patented the device for its potential use as a type of voltage regulator, but apparently did not understand the implications beyond that. Importantly, he demonstrated it at the International Electrical Exhibition in Philadelphia in 1884, at which point a certain William Press brought several of these bulbs back to England and coined the term “Edison effect,” now also known as “thermionic emission,” in a paper he published on the phenomenon the following year. And, of course, as noted, a few decades later Fleming was inspired by it all and eventually did his own thing, as did others like Lee de Forest in the United States and the era of electronics was born.

Vacuum tubes come in two basic types, allowing electricity to be controlled in particular ways. The diode or thermionic valve, invented by Fleming in 1904, consisted of a hollow glass bulb with two basic components: a thin metal wire anode and a plate-shaped cathode. When current was passed through the anode, as indicated in Edison's test, the filament became red hot and began to release electrons through a process called thermionic emission. These electrons were then captured by the cathode, allowing current to flow through the diode. If, however, the current was reversed, the lack of filament at the cathode prevented it from heating up and releasing electrons  meaning that current could not flow in that direction. Diodes thus acted like one way valves  hence their alternative name  and were widely used as rectifiers for detecting radio signals, replacing the previously tempered crystal detector used in commercial radio sets.

The triode or audion, invented by De Forest in 1906, was similar to the diode but with an additional component: a metal grid between the anode and cathode. Applying an electric charge to the grid repels electrons coming from the anode, allowing the number reaching the cathode to be adjusted. This meant that a weaker current could be used to control a stronger one. It could be used to amplify weak signals, such as those from a radio receiver or telephone. De Forest's invention ushered in the modern era of electronics, making possible breakthroughs such as long-distance telephone and radio communications. Triodes were also widely used as electronic switches, being more reliable and less prone to wear than electromechanical relays. In fact, the earliest electronic computers, such as the British Colossus used to break the German Lorentz cipher  and the American Colossus  used to generate ballistics tables for naval guns  used thousands of networked vacuum tubes to perform high-speed calculations.

However, vacuum tubes had several serious drawbacks. For one thing, their filaments needed to be heated up to work, so older electronic devices such as radios and television sets took anywhere from a few seconds to a few minutes to fully power up. They were also fragile, used a lot of electricity, and generated a lot of heat, meaning that early electronic computers required massive air-conditioning plants to keep their processors cool. And when sub-centimeter-long vacuum tubes were developed, these power and heat issues placed a lower limit on the size of electronic circuits. To make such devices truly compact and portable, a new, more compact, and energy-efficient type of electronic switch was needed. Ironically, the solution to this problem would ultimately lie in an older technology. As mentioned at the beginning of the video, early commercial radio sets used a device called a crystal detector to pick up radio signals. Also known as a cat's-whisper detector, this device consisted of a crystal of lead sulfide or galena and a small spring called a cat's-whisper mounted on a pivoted handle. To use this type of radio, the user touched the cat's whiskers to different parts of the galena crystal until they found a spot that corrected the radio signal and allowed it to be heard on headphones.

As you might imagine, the device was difficult to use and took a lot of practice to master. The crystal detector worked by creating a temporary metal-semiconductor junction, also known as a Schottky diode after its discoverer, the German physicist Walter H. Schottky. Galena, along with iron pyrite, carborundum, silicon, germanium, and several other substances, belongs to a class of materials known as semiconductors. Neither perfect conductors like most metals nor perfect electrical insulators, semiconductors can change their electrical properties by treating or doping them with various impurities such as arsenic or phosphorus. Such doping creates either an N-type semiconductor, which has an excess of electrons in the outer shells of its atoms. Or a P-type semiconductor, which has an excess of electrons called electron holes. Sandwiching P and N semiconductors together creates a PN-junction. At the interface between the two semiconductors, the difference in electrical charges causes a so-called diffusion current to flow, in which electrons flow from the N side to the P side and electron holes flow from the P side to the N side. This results in the formation of two adjacent layers of positive and negative transition – called the depletion region.

When an external current is applied from N to P – that is, in the direction of the internal diffusion current  ​​it will flow freely through the diode. If, however, current is applied in the opposite direction, it will cause the depletion region to grow, creating a barrier through which current cannot flow. Thus a PN junction functions much like a vacuum tube diode, allowing current to flow in only one direction. In a metal-semiconductor junction such as a crystal detector, the semiconductor is N-type while the metal acts as a P-type semiconductor, the interface between the two forming a depletion region or Schottky barrier as in a PN junction.

The PN junction diode was discovered in 1939 by Bell Labs researcher Russell Ohl when he accidentally cut off a portion of the silicon ingot at a PN junction and noted its rectifying properties. During World War II, self-made Schottky and PN diodes were developed for use in military radars, since vacuum tubes could not operate at the required frequencies. These devices were the first truly small solid-state electronic components, and pointed to the use of semiconductors to create a new, efficient analog for the triode vacuum tube. Interestingly, the design of a type of semiconductor-based electronic switch now known as the field effect transistor, or FET, was patented as early as 1925 by Austrian-American inventor Julius Lilienfeld. However, because sufficiently pure semiconductors were not available at the time, Lilienfeld was unable to build a working prototype, and his design remained little more than a footnote in the history of electronics. It would not be until after World War II that his ideas would finally become a reality.

The Invention of the Transistor: History, Impact, and Engineering Marvel

This effort resulted in the development of the first practical transistor, spearheaded by Bell Telecom in Murray Hill, New Jersey.

Mervin Kelly, director of research at the Telephone Laboratories. Dissatisfied with the poor performance and reliability of vacuum tubes, Kelly assembled a solid-state physics research team in the late 1930s to come up with a semiconductor-based alternative. The work was halted by World War II, but soon resumed. Oddly enough, the project was a relatively low priority for Bell, as the triode or audion had originally been developed for long-distance telephony. By the late 1940s, the Bell telephone system was based not on vacuum tubes but on complex but reliable electromechanical devices called Stroger switches. A solid-state switch, if practical, was expected to have only limited, specialized applications, such as military radio and radar equipment. Kelly assembled a diverse team of theorists, experimentalists, and engineers, including John Bardeen, Walter Brattain, Robert Gibney, Bert Moore, John Pearson, and the aptly named William Shockley. Of these, it was the trio of Bardeen, Brattain, under Shockley's supervision, that would ultimately make the major breakthroughs. Although the often difficult Shockley preferred to work alone at home, Brattain and Bardeen formed a fruitful partnership, adapting to the freewheeling, anything-goes research culture of Bell Labs by working late into the night without supervision.

The first design the team investigated was proposed by Shockley, and it worked in line with Julius Lilienfeld's 1925 concept. Built around a block of silicon, like a vacuum tube, the device had an anode and cathode—now called source and drainat either end, but instead of a grid, a third electrode called a gate was used to control the flow of electricity through the device. In theory, when current was applied to the gate, the electric field created would prevent electrons from flowing between the source and drain. In practice, however, the design failed to work. Nevertheless, Shockley was convinced that his design was viable, and persuaded Bell Labs to file a patent with him as the sole inventor. To Shockley's dismay, however, Bell had recently discovered Lillian Field's original patent and informed Shockley that his idea was not original. After much experimentation, Walter Brittain determined that the failure of Shockley's design was due to the accumulation of electrons on the surface of the silicon, which was blocking the electric field of the gate. On the advice of Robert Gibney, he and Bardeen tried to solve the problem by soaking the prototype in distilled water, filling the air gap between the gate and the silicon and increasing the strength of the electric field. Amazingly, it actually worked though nowhere near as effectively as the team had hoped. As Shockley later noted:

“This new discovery was generating electricity… Finally, Brittain and Gibney overcame the blocking effect.”

Replacing the water with a chemical called glycol borate produced better results, but the device still had a slow response time and could not handle high frequencies—a critical requirement for use in radio and radar equipment. Eventually, the team abandoned silicon as a substrate and focused instead on germanium, the preparation of which had already been completed for use in diodes. But the material showed the same barrier effect as silicon, and although the team tried countless treatments, such as freezing the germanium in liquid nitrogen, full-scale growth still eluded them.

It was then that a couple of random accidents nudged the team in the right direction. For his latest prototype, Brettain grew a thin layer of oxide on the surface of a germanium crystal and deposited an even thinner layer of gold on top of it, hoping that the oxide would separate the gold from the germanium. At first it seemed to work, but Brettain soon realized that the oxide layer had actually been washed away, meaning the gold was in direct contact with the germanium. This indicated that the device was not working according to the field effect as Shockley had predicted, but some other, as yet unknown phenomenon.

On another occasion, while measuring the amplification or gain in a prototype, Brattain accidentally damaged one of the gate electrodes by touching it to the emitter electrode. But when he placed the emitter closer to the gate electrode, he suddenly observed the advantage the team was looking for. Based on this, Bardeen suggested placing the emitter and gate electrodes extremely close to each other  within 50 micrometers  to enhance the effect. To accomplish this, Brattain wrapped a piece of thin gold foil around the point of a plastic triangle, cut a thin slit in the foil with a razor blade, and forced this pair of closely spaced contacts onto the germanium crystal with a spring. Two electrodes, known as the emitter and collector, were connected to the two halves of the gold foil, while the third was connected to the base of a lead germanium crystal, which was specially prepared because it consists of two layers: an upper P-type layer filled with electron holes and a lower N-type layer with excess electrons. In this configuration, the current flowing from the collector to the base was modulated by applying a current to the emitter.

On December 16, 1947, Breiten and Bardeen first demonstrated their new The design was tested. To their delight, it worked perfectly, exhibiting a 30 percent increase in power and a 15 percent increase in voltage at a frequency of 1,000 Hz. Carpooling home that night, Brittain told his colleagues that they had just performed the most important experiment of their lives and swore them to secrecy until Bell Labs officially announced their discovery. Bardeen, however, could not help sharing the news, telling his wife over dinner that “we discovered something today.” His wife, distracted by the couple’s children, reportedly replied: “That’s good, dear.” In contrast, William Shockley, then on sabbatical in Europe, was furious to discover that not only was he not directly involved in the team’s progress but that they had strayed far from their original field effect concept. It was a bitterness that was to prove surprisingly fruitful.

On June 30, 1948, Bell Labs officially announced the discovery of Brattain and Bardeen, which had by now acquired a new name: transistor. The term had been coined by fellow Bell engineer and part-time science fiction writer John Pierce as a contraction of “transistor.” Unfortunately, however, the announcement of the transistor received little attention in the popular or scientific press. Not only were there few obvious applications for the device, but it was also fragile, temperamental, and difficult to manufacture. Moreover, even its inventors did not quite understand how it worked. Meanwhile, Shockley, inflamed with jealousy and anger, continued his quest to bring his colleagues together. While attending a meeting of the Physical Society in Chicago in late 1947, he began filling his notebook with page after page of detailed notes describing a new type of transistor, one that consisted of a layer of p-type semiconductor sandwiched between two layers of n-type semiconductor. By January 23, 1948, Shockley had come up with a workable design, one that worked like a PN diode but with three terminals: emitter, collector, and base. When a positive current was applied to the base, it disrupted the depletion region between the semiconductor layers by removing excess electrons, allowing current to flow between the emitter and collector. Bardeen and Brittain's transistor worked in a similar fashion, except that the current passed through a thin layer on top of the germanium crystal. A month after Shockley completed his theoretical design, Bell Labs filed four patents for semiconductor amplifiers  both the original point-contact design of Breitling and Bardeen and Shockley’s bipolar junction or NPN transistor.

Although Shockley’s design was successfully demonstrated on April 2, 1950, the first commercial transistors, manufactured by Western Electric in 1951, were of the point-contact type. But while they saw limited use in long-distance telephone switching gear and military equipment, it soon became clear that the junction transistor was far more robust and easier to manufacture, and it became the standard design going forward.

Still, for many years the transistor was a solution in search of a problem. It was not until 1952 that the New York-based firm Sonotone introduced a lightweight transistorized hearing aid  the first consumer product to use the new technology. Two years later, Texas Instruments researcher Gordon Tell discovered that replacing germanium which was unreliable and sensitive to temperature fluctuations with silicon produced even more reliable and robust transistors. That same year, Texas Instruments and Industrial Development Engineering Associates unveiled a ground breaking product: the Regency T-1, the world’s first portable, fully transistorized radio. Despite technical problems, the radio was an immediate hit, selling 150,000 units during its short production run.

It’s hard to overstate the cultural impact of the TR-1 and its descendants. Before that, consumer radios had been bulky, bulky devices confined to the living room of the home. With transistor radios, however, consumers especially teenagers could take their music with them wherever they wanted a capability that profoundly shaped the development of youth culture. The transistor also helped reshape the global economic landscape. As American manufacturers increasingly focused on Cold War military contracts, foreign entrepreneurs saw an opportunity to cash in on the emerging consumer electronics market. Among them were Japanese engineers Masaru Ibuka and Akio Morita, who founded the electronics company Tokyo Teletech in 1946. In 1958, the company changed its name to Sony. Soon, inexpensive Sony transistor radios and television sets began flooding the global market, establishing Japan as the world leader in consumer electronics and finally ending the vacuum tube era.

Meanwhile, the importance of the discoveries of Brittain, Bardeen, and Shockley was finally recognized when, in 1956, the three shared the Nobel Prize in Physics for "their research on semiconductors and their discovery of the transistor effect." But their joy was short-lived, as by then Shockley's relentless pursuit of sole credit for the invention of the transistor had torn the team apart. Shortly after receiving the Nobel Prize, Shockley moved to Palo Alto, California, and founded Shockley Semiconductor Laboratories, the first tech company to be known as Silicon Valley. But while Shockley’s power initially attracted the best and brightest to his company, his difficult personality and brutal management style soon drove them away.

A group of exiles known as the “Traitorous Eight” went on to found Fairchild Semiconductor, which produced the world’s first practical integrated circuit, or microchip, in 1959. Two of the eight, Bob Noyce and Gordon Moore, later founded Intel Corporation, which is today one of the world’s largest manufacturers of microprocessors. After losing his company, in 1963 Shockley accepted a position as a professor of engineering and applied science at Stanford University. And it was here that his career took a dark turn. Despite not having a degree in genetics or related subjects, Shockley began to promote sound scientific theories about race, intelligence, and eugenics, declaring, for example:

"My research leads me inevitably to the opinion that the major cause of the intellectual and social deficits of the American Negro is hereditary. And is essentially racially genetic and, thus, largely untreatable by practical improvements in the environment."

Shockley was such a believer that miscegenation AKA race mixing—posed an existential threat to the United States that he ran as a Republican candidate in the 1982 Senate election on a single-issue platform of opposition, referring to the "dysgenic threat" posed by African-Americans and other minority groups. He came in eighth in the primary, receiving a paltry 0.37 percent of the vote. By the time Shockley died in 1989 at the age of 79, he had become a pariah, the Los Angeles Times reported in its obituary:

“He went from being a physicist with impeccable academic credentials to an amateur geneticist, becoming a lightning rod whose ideas sparked campus protests.”

Meanwhile, the co-discoverers of the transistor fared little better. In 1951, John Bardeen left Bell Labs for the University of Illinois, where he began investigating the phenomenon of super conductivity the ability of some materials to achieve zero electrical resistance when cooled to extremely low temperatures. This ground breaking work earned him the 1972 Nobel Prize in Physics, making him the only person in history to win the award twice. He died in 1991 at the age of 82. Walter Bretagne continued to work at Bell Labs until 1967 before joining the faculty at Whitman College in Walla Walla, Washington, where he remained until his retirement in 1976. He died in 1987 at the age of 85. He benefited financially from his discovery.

In any piece discussing the origins of the transistor, we would be remiss not to point out that Bardeen, Bretagne, and Shockley were not the only people working on the transistor. At the same time that semiconductor research was booming at Bell Labs, Herbert Matari and Heinrich Welker, German physicists working at the Compagnie de Freies et Cinécois in Paris, were investigating similar germanium-based modulation devices. In June 1948, they succeeded in creating a working point-contact transistor similar to the 1947 prototype of Bardeen, Brittain, and Shockley. However, shortly thereafter, Matari and Welker were dismayed to learn that Bell Labs had already beaten them to the punch. Nevertheless, in 1949 their employer became the first company in Europe to commercially produce transistors. It should also be noted that less than a decade later, several inventors, including Ian Ross, John Wallmark, and Muhammad Atala, developed practical field-effect transistors, or FETs. Today, FETs specifically metal-oxide-semiconductor transistors or MOSFETs are the most widely used transistor type in the world, particularly suited to making small In fact, while the earliest commercial transistors were about a centimeter in size, modern integrated circuit transistors are so small that at the time of writing this piece, the world's most powerful single computer chip - the Cerebras Wafer Scale Engine 2 - contains an unimaginable 2.6 trill of them.