John D. Cressler
©SHUTTERSTOCK.COM/GOLAM-ROBBANY
History is the essence of innumerable biographies.
—Thomas Carlyle
This article traces the history to the invention/discovery of the transistor. Seventy-six years of the transistor. My, my, time flies. Such a remarkable little piece of quantum physics in action. The transistor was invented/discovered on 16 December 1947, then introduced to the world on 23 December 1947 [2], an Earth-changing moment. It was roughly the size of your thumbnail. In 2023, transistors are virtual sized and speed-of-light fast, and, importantly, they cleverly possess, just like the original, that unique golden attribute of amplification, making tiny voltages and currents larger. There are over 1024 transistors on Earth in 2023, made possible by the jaw-dropping exponential growth patterns embodied in Moore’s law. It is instructive to compare the first transistor with a contemporary embodiment (Figures 1 and 2).
Figure 1. A scaled replica of the world’s first point contact transistor, using authentic materials. This one was made by Milad Frounchi, in 2021. Frounchi is one of the author’s former Ph.D. students, and he has a love of crafting intricate miniatures.
Figure 2. A scanning electron microscope cross section of a modern SiGe bipolar CMOS technology, showing an SiGe HBT, CMOS transistors, and the metalization superstructure. (Source: P. Chevalier, STMicroelectronics; used with permission.)
Transistors are ubiquitous to modern life, whether seen or unseen by both purveyors and consumers of technology. Surely the word transistor should be added to the vocabulary of every single person on Earth. The simple fact is that all modern technology, without exception, from smartphones to automobiles to planes to the Internet to GPS, would instantly cease to function if the transistor were subtracted from the planet. Want to decode the human genome, use CRISPR to cure a disease, or build a better crop, develop a messenger ribonucleic acid vaccine for a pandemic, hone artificial intelligence and virtual reality without a transistor? Never gonna happen! In fact, in terms of its impact on the trajectory of civilization writ large, one could fairly argue that the invention of the transistor is the most important invention/discovery in human history. Bold words but quite defensible [1].
To my mind, there are four compelling reasons to examine the historical foundations of any given technological field:
From a broad-brushed historical perspective, many aspects of the development of microelectronics technology are strikingly unusual. For instance, most technologies have traditionally proceeded from “art†to “science,†rather than the other way around. In the steel industry, for instance, literally centuries of empirical craftsmanship (the “artâ€) transpired before even the most rudimentary scientific underpinnings were established (the “scienceâ€). People knew how to produce high-quality steel and fashion it into all sorts of sophisticated objects, from tools to cannons, long before they understood why steel worked so well. This knowledge base was largely empirically driven—as they say, practice makes perfect. Part of this inherent difficulty in applying science to steel production lies in the exceeding complexity of the materials involved. Steel is simply a very complicated material, chock-full of nuances and unknown variables (this is no longer true, obviously). Microelectronics, by contrast, represents one of the rare instances in the history of technology in which “science preceded the art†[3].
Part of this difference between microelectronics and all other technologies lies in the fundamental problems associated with the materials involved. For microelectronics, we are dealing with a near-perfect single crystal of regularly arranged atoms of a single element—silicon (Si)—about as simple and ideal a material as one can imagine to apply the scientific method to. By most accounts, and for obvious reasons, today, Si is far and away the best understood material on Earth. In such “simple†problems, trivial (literally, back-of-the-envelope) theory can often work astoundingly well in capturing reality. For instance, imagine introducing a tiny number of phosphorus atoms into Si (e.g., add one phosphorus atom for every 100 million Si atoms). Question: How much energy does it take to release the extra electron bound to the incorporated phosphorus atom into the crystal (this is called the dopant ionization energy and is very important information for building transistors and circuits)? Hint: A scratch of the head and a puzzled look would be appropriate here for most readers. Answer: This problem can be well described by a simple “toy model†of a hydrogen atom (the Bohr model, 1913), something every first-year college science and engineering student learns, and in 2 s (OK, three) of simple calculations, we have an answer accurate to within a factor of three. Correct answer? It’s 45 meV. Toy model answer? We have 113 meV. This accuracy is rather amazing if you stop and think about it, given the complex quantum mechanical nature of the actual problem involved. Science works quite well in such idealized venues, and, in the end, this turns out to be pivotal to the ultimate success of microelectronics technology because, as a circuit design engineer, for instance, I do not have to stop and worry about performing a detailed first-principles solution to Schrödinger’s equation, the pesky (read: exceedingly difficult to solve) workhorse of quantum mechanics, to know how to bias my transistor in the electronic circuit I am constructing. If I did, there clearly wouldn’t be many smartphones and computers around.
It is interesting that microelectronics technology, in fact, has followed the popular (but, alas, commonly misperceived) direction of technological innovation—first discover the science, and when the science is mature, then hand it off to the engineers so that they can refine and develop it into a viable technology for society’s happy use. A glance at the historical record indicates that this common view of how technological innovation should ideally proceed, however appealing, is rarely borne out in practice. Microelectronics is one of the very few exceptions [4]. The transistor was born from a rich legacy of science but virtually nonexistent art. By art, in this context, I mean the accretion of skills, techniques, and engineering approaches that would permit the fabrication of microscopic structures called for by the transistor inventors for feasibility demonstrations and design engineers for subsequent refinements. Just who exactly were the purveyors of the requisite art of this fledgling microelectronics empire? Interestingly, and unique at least to the time, these individuals were trained scientists (physicists, primarily) but working principally as engineers, all the while searching for (profitable) inventions. They were a new breed, a fascinating amalgam of scientist–engineer–inventor.
What exactly drove the world inexorably to the transistor and why? For brevity, I omit the fascinating trajectory of events and discoveries that led us to the transistor and save it for another day [1].
After World War II, the famous “Transistor Three†assembled at Bell Telephone Laboratories (“Bell Labsâ€), in Murray Hill, NJ, USA (Figure 3), and began their furious search for a solid-state amplifying device, a semiconductor triode (our soon-to-be transistor) [5], [6], [7]. Hired by Director of Research Mervin J. Kelly (later, president of Bell Labs), in 1936, William Shockley, a theoretical physicist, in 1945 became group leader of a new “semiconductor†group containing Walter Brattain, an experimental physicist extraordinaire (who joined Bell Labs in 1929), and John Bardeen, a theoretical physicist (who joined Bell Labs in 1945). Kelly’s dream, put to Shockley as a provocative challenge of sorts for his new team, was “to take the relays out of telephone exchanges and make the connections electronically.†Kelly was after a replacement of the notoriously unreliable mechanical telephone relay switch but could have equivalently asked for a replacement of the equally unreliable vacuum tube amplifier of radio fame, the electrical equivalence of a solid-state amplifier and electronic switch being implicit. Importantly (and, sadly, quite unusual by today’s standards) Kelly assembled this “dream team†of creative talent and then promptly gave it carte blanche over resources and creative freedom, effectively saying “I don’t care how you do it or how much money you spend, but find me an answer, and find it fast.â€
Figure 3. The Bell Labs facility.
During the spring of 1945, Bell Labs issued an important authorization for work explicitly targeting fundamental investigations into a half dozen classes of new materials for potential electronics applications, one of which, fortuitously, was semiconductors [principally, Si and germanium (Ge)]. The Transistor Three all had some experience with semiconductors and, thus, logically focused their initial efforts on amplification using semiconductors, based on Shockley’s pet concept of a capacitor-like metal–semiconductor structure not unlike that of a modern MOSFET. This search direction culminated in more than a few of what Shockley termed “creative failures.†The reason such devices failed was soon understood (by Bardeen) to be related to surface defects in the semiconductor crystal itself.
Armed with Bardeen’s theory, Bardeen and Brattain began to look for ways to effectively “passivate†(remove the defects from) the surface of the Si crystal, into which Brattain had stuck two metal cat’s whiskers for electrodes. Unfortunately, condensation kept forming on the electrodes, effectively shorting them out. In a creative leap, on 17 November 1947, Brattain dumped his whole experiment into nonconducting (distilled) water (he knew a vacuum would have worked better but later said that it would have taken too long to build). To his amazement, he thought he observed amplification. When Bardeen was told what had happened, he thought a bit and then, on 21 November, suggested pushing a metal point into the semiconductor surrounded by a drop of distilled water. The tough part was that the metal contact couldn’t touch the water; it could touch only the semiconductor. Ever the clever experimentalist, Brattain later recalled, in 1964 [5], “I think I suggested, ‘Why, John, we’ll wax the point.’ One of the problems was how do we do this, so we’d just coat the point with paraffin all over, and then we’d push it down on the crystal. The metal will penetrate the paraffin and make contact with the semiconductor, but still we’d have it perfectly insulated from the liquid, and we’ll put a drop of tap water around it. That day, we in principle, created an amplifier.â€
Once they’d gotten slight amplification with that tiny drop of water, Bardeen and Brattain figured they were onto something significant. They experimented with many different electrolytes in place of the water and consistently achieved varying degrees of amplification. On 8 December, Bardeen suggested that they replace the Si with (in retrospect) less defective Ge. They suddenly achieved an amplification of 330× but, unfortunately, only at very low frequencies (rendering it unsuitable for the envisioned applications). Bardeen and Brattain thought the liquid might be the problem, and they replaced it with Ge dioxide. On 12 December, Brattain began to insert the point contacts. To his chagrin, nothing happened. In fact, the device worked as if there were no oxide layer at all. As Brattain poked the gold contact repeatedly, he realized that no oxide layer was present; he had washed it off by accident. Furious with himself, he serendipitously decided to go ahead and play a little with the point contacts anyway. To his intense surprise, he again achieved a small amplification but, importantly, across all frequencies. Eureka! The gold contact was effectively puncturing the Ge and passivating the crystal surface, much as the water had.
During that month, Bardeen and Brattain had managed to achieve a large amplification at low frequencies and a small amplification for all frequencies, and now they cleverly combined the two. They realized that the key components to success were using a slab of Ge and two gold point contacts located just fractions of a millimeter apart. Now suitably armed, on Tuesday afternoon, 16 December 1947, Brattain put a ribbon of gold foil around a plastic triangle and cut it to make the point contacts. By placing the vertex of the triangle gently down on the Ge block to engage the point contacts, he and Bardeen saw a fantastic effect: a small signal came in through one gold contact (the electron “emitterâ€) and was dramatically amplified as it raced through the Ge crystal (physically the “base†of the contraption) and out the other gold contact (the electron “collectorâ€). Success!
The first point contact semiconductor amplifier had been invented, or discovered, depending on your point of view (Figure 4). I think of it as an invention/discovery. Bardeen and Brattain’s seminal paper on their transistor (remarkably, only one and one-half pages long; refer to Figure 5) was published in Physical Review, on 15 July 1948 [2]. Hint: there was no IEEE Electron Device Letters.
Figure 4. (a) The famous point contact transistor, the first solid-state amplifying device, invented by Bardeen and Brattain. Bardeen and Brattain discovered that by placing two gold contacts close together on the surface of a crystal of Ge through which an electric current was flowing, a device that acted as an electrical amplifier was produced. (Source: Alcatel-Lucent; used with permission.) (b) A schematic of the device. See also the companion article in this issue by Kaufman and Dallesasse.
Figure 5. The paper published by Bardeen and Brattain debuting their invention of the point contact transistor to the world. They acknowledge Shockley’s contribution in the last paragraph.
The name transistor was coined by J.R. Pierce, following an office ballot (read: a betting pool). Important: all cool widgets must have cool widget names. He started with a literal description of what the device actually did electrically, a “transresistance amplifier,†which he first shortened to “transresistor†and then, finally, to “transistor†[5]. Finito, it stuck.
After an additional week of experimental refinement, the formal transistor demonstration was repeated for Shockley’s semiconductor group (Gibney, Shockley, Moore, Bardeen, and Pearson, with Brattain at the wheel) and, importantly, two of the Bell Labs’ “brass†(a research director, R. Bown, and Shockley’s boss, H. Fletcher—ironically, Kelly, who launched it all, was not informed for several more weeks), on Tuesday afternoon, 23 December 1947, just before everyone left for the Christmas holidays (it was already snowing), which is now regarded as the official date stamp for the invention of the transistor and the birth of the Information Age. A pivotal moment in human history, and worth remembering. I certainly demand that of my students.
In a telling comment, Shockley later said, “My elation with the group’s success was balanced by the frustration of not being one of its inventors†[4], [8]. It is ironic, then, that the most famous picture of the event contains all three men, with Shockley front and center, hovering over the transistor as if it were his own baby (Figure 6). On the famous portrait of the Transistor Three, Nick Holonyak, in an interview with Frederick Nebeker, on 22 June 1993, said, “[John Bardeen] said to me, ‘Boy, Walter really hates this picture.’ I said to him at the time, ‘Why? Isn’t it flattering?’ That’s when he made this face at me, and shook his head … He said to me, ‘No. That’s Walter’s apparatus, that’s our experiment, and there’s Bill sitting there, and Bill didn’t have anything to do with it.’â€
Figure 6. The famous Transistor Three: William Shockley (seated), Walter Brattain (right), and John Bardeen (left). (Source: Alcatel-Lucent; used with permission.)
Meanwhile, Shockley spent New Year’s Eve alone in a hotel in Chicago, IL, USA, where he was attending the American Physical Society Meeting. He spent that night and the next two days essentially locked in his room, working feverishly on his idea for a new transistor type that would improve on Bardeen’s and Brattain’s point contact device. Why? Primarily because he felt slighted. It has been pointed out that perhaps the most important consequence of the invention of the point contact transistor was its direct influence on Shockley as an incentive to discovery. “This experience and the resulting emotion wound Shockley’s spring so tightly that in the following 10 years, he was the author of the most remarkable outpouring of inventions, insights, analyses, and publications that [any] technology has ever seen. It is only a slight exaggeration to say that he was responsible for half of the worthwhile ideas in [all of] solid-state electronics†[3].
Shockley believed he should have received credit for the invention of the transistor, given that his original idea of manipulating the surface of the crystal set the stage for Bardeen and Brattain’s eventual success … and, of course, because he was the boss. Not surprisingly, the Bell Labs lawyers (and management) didn’t agree. And so, over the New Year’s holiday, Shockley fumed, scratching page after page into his lab notebook, primarily focusing on his new idea for constructing a transistor from a “sandwich†of different semiconductor layers all stuck together. After some 30 pages of scribbling (refer to Figure 7), the concept hadn’t quite gelled, and so Shockley set it aside.
Figure 7. Page 128 of Shockley’s technical journal, showing his idea of the BJT. (Source: Alcatel-Lucent; used with permission.)
As the rest of the semiconductor group worked feverishly on improving Brattain and Bardeen’s point contact transistor, Shockley remained aloof, concentrating on his own ideas, secretive to the extreme. On 23 January, unable to sleep, Shockley sat at his kitchen table early in the morning, when the lightbulb suddenly switched on. Building on the semiconductor “sandwich†idea he’d come up with on New Year’s Eve, he became quickly convinced that he had a solid concept for an improved transistor. It would be a three-layered device. The outermost pieces would be semiconductors with too many electrons (n-type), and the piece in the middle would have too few electrons (P-type). The middle semiconductor layer would act like a faucet: as the voltage on that part was adjusted up and down, he believed it could turn current in the device on and off at will, acting as both a switch and an amplifier.
Predictably, Shockley didn’t breathe a word. The basic physics behind this semiconductor amplifier was very different from Bardeen and Brattain’s device because it involved current flowing directly through the volume of the semiconductors, not along the surface, and Shockley proceeded to derive its operational theory. On 18 February, Shockley learned that his idea should, in fact, work. Two members of the group, Joseph Becker and John Shive, were conducting a separate experiment whose results could be explained only if the electrons did, in fact, travel right through the bulk of a semiconductor, the linchpin to the practicality of Shockley’s idea. When they presented their findings to the rest of the group in their normal weekly team meeting, Shockley literally leaped from his seat and, for the first time, shared his idea for a “sandwich†transistor. It became painfully obvious to all that Shockley had been hoarding his secret for weeks and would likely have continued to do so for some time. In Shockley’s own words, “Shive forced my hand†[3]. Bardeen and Brattain sat stunned as they realized they had been deliberately kept in the dark.
Needless to say, Shockley was quick to file the now immortal patent for his “bipolar junction transistor†(Figure 8): U.S. patent 2,502,488, filed in June 1948 and issued 4 April 1950. Note the solo authorship. Shockley had the last laugh. Interestingly, the BJT patent also (almost casually) mentions the basic idea of the “heterojunction†bipolar transistor using a wide-bandgap emitter (Si), with a narrow-bandgap base and collector (Ge), anticipating the now enormously important field of bandgap-engineered devices. My own field. With both an idea and a basic theory of operation in place, it is ironic that the requisite art of making Shockley’s BJT did not yet exist, and thus, the BJT, ultimately a far more manufacturable and important transistor than the original point contact device, was not actually demonstrated until 12 April 1950 and in an article published in 1951 [9].
Figure 8. Page 1 of Shockley’s seminal BJT patent. (Source: U.S. Patent Office; used with permission.)
Brattain, Bardeen, and Shockley (justifiably, in my view) shared the Nobel Prize for physics in 1956 for their collective contributions in inventing their respective transistors (my guess is that they didn’t chum around afterward in a three-way backslapping celebration). Post transistor, Brattain went on to finish his career at Bells Labs, but Bardeen left Bell Labs in 1951, anxious to pursue different theoretical interests, culminating in a second Nobel Prize, for his theory of superconductivity.
After Bardeen and Brattain’s transistor patent was safely filed, on 17 June 1948, Bell Labs finally prepared to announce its landmark discovery to the world. The announcement was to be a two-pronged assault: 1) in the last week of June, Shockley called the editor of Physical Review and told him he was sending three papers that (hint, hint) needed to appear in the 15 July issue (this less-than-three-week publication cycle must be a record for a technical journal). One was the fundamental transistor paper [2], one offered an explanation of the observed transistor action (also by Brattain and Bardeen), and a third (now largely forgotten) was authored by Pearson and Shockley (go figure). 2) Bell Labs scheduled a major press conference in New York for 30 June. Not surprisingly, a mandatory military briefing was held first, on 23 June, with all in attendance forced by Bell Labs President Oliver Buckley to raise their right hand and swear that they would say nothing until 30 June (I’m not joking). The plot thickens. On Friday, 25 June, Admiral Paul Lee, chief of naval research, called Buckley and told him that the Navy had, in fact, already made a similar discovery, and he wanted to make the 30 June spectacle a joint Bell Labs–U.S. Navy announcement. Major panic attack! The next day, Shockley and company, armed with a cadre of patent lawyers in tow, met with the Navy, and after an intense line of questioning of engineer Bernard Salisbury by Shockley (you can easily visualize this), the Navy backed off, ultimately conceding that the Salisbury gadget was not, in fact, a transistor and that the Bell Labs team had been first. Whew!
The press conference went on as planned as a Bell Labs solo act. Sadly, however, with Brown making the formal announcement and the ever-entertaining Shockley selected for fielding all the reporter’s questions, the seminal contributions of Bardeen and Brattain were not prominently featured in the limelight. Reactions from the popular press to the transistor were decidedly lukewarm, but Bell Labs was not done. The next step (in hindsight, exceptionally shrewd) was to send out hundreds of letters, not to the press but to scientists, engineers, and radio manufacturers, inviting them to Bell Labs, on 20 July, for a demonstration of the new widget. The reception to this event was anything but mixed. Wowed by the discovery, requests for sample transistors began pouring in from all over the world. Kelly once again acted wisely, quickly forming a brand-new Bell Labs group, headed by Jack Morton, aimed explicitly at developing the technological infrastructure for manufacturing transistors in volume—the requisite “art,†if you will. By mid-1949, after significant sweat, over 2,700 “Type-A†point contact transistors had been produced and distributed to interested parties [5].
Fundamental problems with transistor reliability (at the time, little better than the vacuum tube competition) and control of performance parameters, however, soon forced Morton’s team to embrace Shockley’s BJT as the preferred transistor architecture for mass production (surely Shockley was smiling by now), and progress then came rapidly (Figure 9). Western Electric was the first company selected to manufacture transistors, paying a US$25,000 patent licensing fee for the privilege. All companies agreeing to pay this (in hindsight, ridiculously cheap) fee were invited to attend an exclusive “find out how we make ‘em†meeting at Bell Labs in the spring of 1952, and representatives from 26 U.S. and 14 foreign companies were in attendance. Nineteen fifty-three was proclaimed the “Year of the Transistor†by Fortune magazine. To place things in perspective, the combined transistor production from U.S. companies in 1953 was about 50,000 a month, compared with nearly 35 million vacuum tubes, but Fortune already glimpsed a bright future for the transistor and the potential for producing “millions a month†[5]. The selling price for a single transistor in 1953? About US$15.
Figure 9. The (a) first BJT and (b) first MOSFET. (Source: Alcatel-Lucent; used with permission.)
End of story? Nope. You might wonder what comes next that leads us from Ge back to Si and to produce the modern IC, Moore’s law, the microprocessor, and the world we know today. Alas, I am out of room for this issue. Stay tuned for the next installment. Trust me, it is a fascinating story, full of important takeaways.
Much of the text in this article owes a debt to the author’s book Silicon Earth: An Introduction to Microelectronics and Nanotechnology [1], which is intended for general audiences and used by the author in a course for undergraduates of all majors at the Georgia Institute of Technology.
John D. Cressler (cressler@ece.gatech.edu) is a Regents Professor and the Schlumberger Chair Professor in Electronics in the School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA 30332 USA.
[1] J. D. Cressler, Silicon Earth: Introduction to Microelectronics and Nanotechnology, 2nd ed. Boca Raton, FL, USA: CRC Press, 2016.
[2] J. Bardeen and W. H. Brattain, “The transistor, a semiconductor triode,†Physical Rev., vol. 74, no. 2, pp. 230–231, Jul. 1948, doi: 10.1103/PhysRev.74.230.
[3] R. M. Warner Jr., “Microelectronics: Its unusual origin and personality,†IEEE Trans. Electron Devices, vol. 48, no. 11, pp. 2457–2467, Nov. 2001, doi: 10.1109/16.960368.
[4] R. M. Warner Jr. and B. L. Grung, Transistors: Fundamentals for the Integrated-Circuit Engineer. New York, NY, USA: Wiley, 1983.
[5] M. Riordan and L. Hoddeson, Crystal Fire (Sloan Technology Series). New York, NY, USA: Norton, 1998.
[6] T. R. Reid, The Chip. New York, NY, USA: Random House, 2001.
[7] P. K. Bondyopadhyay, P. K. Chaterjee, and U. Chakrabarti, “In the beginning [junction transistor] ,†Proc. IEEE, vol. 86, no. 1, pp. 63–77, Jan. 1998, doi: 10.1109/5.658760.
[8] W. Shockley, “How we invented the transistor,†New Scientist, vol. 21, pp. 689–691, Dec. 1972.
[9] W. Shockley, M. Sparks, and G. K. Teal, “p-n junction transistors,†Physical Rev., vol. 83, no. 1, Jul. 1951, Art. no. 151, doi: 10.1103/PhysRev.83.151.
Digital Object Identifier 10.1109/MED.2023.3267740
Date of current version: 28 June 2023
