Transistors
by Charles McNeil VE3HBB
Nov 14, 2002
The idea to offer this presentation came to me around a year ago when I first encountered the book “Crystal Fire, The Birth of the Information Age” by Michael Riordan and Lillian Hoddeson. This is a fascinating book that traces the development of the semi-conductor. It also draws the readers’ attention to the personalities of the individuals involved in the early work. In my opinion, too often we tend to examine the technology as if it was developed without human intervention. The human drama is often neglected.
Consider this presentation, then, as a book review. I cannot in the available time treat the book in its entirety. Further, I intend to comment on some of the ethical issues raised, and my commentary will go a little bit beyond what is found between the covers. Finally, this is only one of a number of fine books all of which deal with the history of science and technology.
This is NOT to be a technical discussion of transistors, etc. It is more of a historical treatment of the processes which brought the transistor into being. However, it was suggested that I include a brief overview of how transistors do what they do. So, let’s begin with a description of the functioning of a typical junction transistor. Please be warned, that this is a very elementary description. I am not an engineer nor am I a physicist. I provide this merely to indicate to anyone here lacking this knowledge what the originators of the transistor were up against as they carried out their work. For those seeking a more technical description of semiconductor physics, I would suggest the following URL: http://www.engplanet.com/redirect.html?2436
To begin, imagine a piece of exotic metal such as germanium. If a high enough voltage is applied to this material, electrons will flow through it. In this way, the germanium behaves much like any other metal. However, under ordinary circumstances, germanium or silicon are poor conductors of electricity.
Now add in a trace amount of some other material. This process is known as doping. The materials used are, from the perspective of the crystal lattice, impurities. Ensure that the material is able to increase the number of free electrons present within the crystalline structure of the germanium. Now, the material becomes a better conductor of electricity because there is a surplus of electrons which are not locked tightly into the crystalline matrix of the material.
We will call these “donor electrons”, and they are considered to be the majority intelligence carriers.
Adding another impurity can steal electrons from their positions in the crystalline matrix. These acceptor atoms create a surplus of holes, or, relatively positive regions in the semiconductor. They are, in essence, spaces in the matrix where electrons would have at one time resided. In this case, the majority carriers are the holes. Note that holes travel in a direction opposite to electron flow.
We will call the former material “N” type material and the latter “P” type material. Now, if we bond together a quantity of N type material with a quantity of P type material, we end up with a semiconductor diode.
If we apply a voltage of a given polarity to this device, current will flow. If we reverse the polarity, current will not flow. This is useful for the rectification of signals.
Were we to bond another quantity of material to the diode, we have a transistor. For example, image a piece of N type material bonded to a piece of P type material, and then another piece of N type material attached to the other end. The order will then be N-P-N and the transistor will be an NPN transistor.
We will term one piece of N material the emitter, the P slice we will call the base, and the other end, N type material the collector. At each junction between N and P type material, electrons will exchange positions. This creates a barrier potential blocking the movement of free electrons from one section of the transistor to another. As long as the conditions exists in which no voltages are applied to the device, no current will flow. However, if we forward bias the junction with an adequate voltage, the barrier will be overcome, and current will begin to flow.
How is this useful? Think about a vacuum tube, for a moment. The cathode is similar to the emitter, the grid is analogous to the base and the plate is equivalent to the collector. Small changes on the grid will regulate the greater current flow through the tube. As is the case with the tube, a small signal applied to the base of a properly biased transistor will control a much larger flow of current through the transistor. In this manner, amplification becomes possible. Essentially, the barrier potentials within the device are managed or modulated by the signal appearing on the base section. PNP transistors work in the same manner, however, the polarities are opposite to those of the NPN device.
Transistors have many uses and amplification is but one. They can also be used as switches, or combined in a variety of ways to provide a number of functions. Again, consider this to be a quick and dirty description of what is an incredibly complex process. Now, lets go on.
o This presentation will attempt to trace, in brief, the development of the commonplace transistor. From this device, we have witnessed the emergence of the microchip. VLSI these days is capable of laying down millions of transistors on tiny wafers of semi-conductor substrate. We will see that the personalities involved in this drama, as much as the science played a determining role in the development of these devices.
o I will also discuss pseudoscience as espoused by William Shockley, the man usually identified as the inventor of the transistor. In reality, the transistor was the work of many people both sung and unsung. The other two principals were John Bardeen and Walter Brattain.
The term “Transistor” originated with John Pierce, a member of Shockley’s team. When asked by Walter Brattain what to call the device, he stated that vacuum tubes had a characteristic “trans-conductance.” The semi-conductor equivalent is “trans-resistance.” Finally he uttered “trans-resistor” or more simply put “transistor.”
So, what are the characteristics of transistors, as we know them?
§ Small size (miniaturization)
§ Cool running
§ Lower energy requirement
§ Light
§ Less noise
§ Capable of VLSI
§ Easy to work with
§ Ubiquitous
Imagine for a moment the world before 1947. This was a world without transistors . . .
§ no advanced computers
§ ineffective or non-existent space program
§ electronic devices would exhibit higher “mean-time to failure” rates
§ Bill Gates: “Without the invention of the transistor, I’m quite sure that the PC would not exist as we know it today”
In December of 1947 the three physicists, demonstrated for the first time a point-contact semi-conductor amplifier. This was not an elegant device!
Imagine a plastic wedge sporting a thin piece of gold foil. This was split down the middle and the entire affair was pressed down onto a lump of germanium. It was held in position by a spring fashioned from a paperclip. A pair of plastic clamps provided further stability. From the foil snaked leads connecting the transistor to other apparatus needed to make the device work and to derive test data. This was a transistor in the raw.
When run, the amplifier provided gain! The vacuum tube had been superseded by an altogether new technology. That the tube held out for years after is of no consequence. Its day had passed.
Let’s turn back the calendar a few years and have a look at the three men who were the driving force in the development of this new device.
William Shockley (1910-1989)
The director of the transistor development project at Bell Laboratories, Dr. William Shockley’s research in the behavior of electronics in crystals introduced him to Bardeen and Brattain, who were hired to assist him in his quest to construct a working transistor. Spurred on by their demonstration of a working point-contact transistor, Shockley envisioned the junction transistor, which became the fundamental structure of transistor developments to come. Shockley succeeded in the development of the junction transistor. This was a more durable and dependable device and allowed the transistor to be easily manufactured. Shockley was very interested in the development of the FET or Field Effect Transistor.
Many attempts to build a working prototype were undertaken and eventually the FET was to become reality. Shockley, however, was not to receive credit for this development.
The idea of a Field-Effect Transistor was initially the work of an obscure researcher. In 1926 Julius Lilienfeld, a Polish-American physicist filed the first of three patents on semi-conductor devices. A US patent was issued in 1930 with two others following soon behind.
Unfortunately for Shockley, Bell Labs determined that his ideas were not original after all. It was ironic that Brattain and Bardeen’s designs were sufficiently original to warrant the award of a patent. They had introduced an original means by which electrical fields could be introduced into a semi-conductor device. Shockley never got over the feeling that he had been let down and slighted by his company and colleagues.
Shockley was born in London in 1910 and was raised in Palo Alto. First home-schooled, Shockley later attended Palo Alto Military Academy and then Hollywood Highschool. He later received his Ph.D. in solid-state physics from the Massachusetts Institute of Technology in 1932 and joined the staff of Bell Laboratories in Murray Hill, NJ, in 1936.
At Bell Labs, he initially went to work within the vacuum tube division, but before a year passed Shockley pressed his management to resume his research on the behavior of electrons in crystals, “and the management policy was flexible enough to allow me to make the change.”
During World War II, he served as director of research for the Antisubmarine Warfare Operations Research Group of the US Navy. He worked on developing an understanding of how sound waves propagate in water. After the war, he returned to Bell Laboratories as co-head of a solid-state research group. Shockley: “and I set as one important goal of the group the making of solid-state amplifier structures that would work.”
It is interesting to note that Shockley’s intelligence was assessed in childhood. His IQ was set at 129. Shockley was not a genius, but was a person of higher than average intelligence, as it was understood at that time. As I will mention toward the end of this presentation, Shockley became increasingly obsessed with intelligence and race, considering his views on the so-called genetic inferiority of some so-called races to supersede his accomplishments in solid-state physics. This is an excellent example of pseudo-science at work.
Shockley left Bell Labs in 1955 to establish Shockley Semiconductor Laboratory (part of Beckman Instruments, Inc.), an effort that was instrumental in the birth of Silicon Valley and the electronics industry. Shockley was a difficult and unstable employer. He was increasingly worried that his employees were conspiring against him and went so far as to insist that his entire staff be assessed on a polygraph, or, lie detector. As a result, a number of his former employees left his firm to found what later became Intel, the most successful microprocessor company in the world.
Finally, Shockley became a distinguished professor of electrical engineering at Stanford University.
He died in 1989 at the age of 79.
Walter H. Brattain (1902-1987)
The eldest of the three and an ingenious experimenter, Dr. Walter H. Brattain’s creativity and persistence enabled the team to triumph over difficult technical obstacles to demonstrate the transistor effect. Indeed, when he joined Bell Labs the organization was only four years old!
Brattain, born in Amoy, China and raised in Washington State, received his Ph.D. from University of Minnesota in physics. He was a distinguished member of technical staff at Bell Labs from 1929 to his retirement in 1962. From 1962 to 1972 he was
a professor and visiting lecturer at his alma mater, Whitman College in Walla Walla, Washington. He was also a visiting lecturer at Harvard University, the University of Minnesota, and the University of Washington.
During his long and distinguished career, Brattain’s chief field of research involved investigations into the surface properties of solids, particularly the atomic structure of conductive material at the surface, which usually differs from its atomic structure in the interior.
Essentially, surfaces of conductors are suffused with a “skin” of free electrons that are in constant motion. The addition of energy in the form of heat, for example, makes the electron flux more pronounced. Our familiar “skin effect” in conductors is evidence of this phenomenon. Deeper in the conductor are found fewer free electrons. Hence the materials there are more stable – the electrons are more likely to be fixed and fewer electrons will flow from atom to atom.
Based on this, Brattain also discovered the photo effect at the free surface of a semiconductor and was instrumental in work leading to a better under-standing of the surface properties of germanium..
He said that after he and a fellow worker, J. A. Becker had looked at using a copper oxide rectifier as the basis of a triode, “It is an understatement to say that the results did not look promising. So I was somewhat amused when, a year or so later, Shockley came to me with an idea of making an amplifier out of copper oxide.” Dr. Brattain tried, but he admitted, “This attempt was not successful.” He noted, “The research work to understand what was really going on in the simplest semiconductors, silicon and germanium, finally resulted in the breakthrough,” and perhaps not a minute too soon, since he admitted, “after fourteen years of work I was beginning to lose faith. But I never felt any pressure from management to discontinue work or to change fields.”
In 1937, when it was announced that another Bell Labs researcher, C. J. Davisson, won the Nobel Prize, Dr. Brattain was watching as the news services took pictures and movies of him. During a break, Davisson walked over to him and said, ‘don’t worry, Walter, you’ll win one someday.’ Little did I know that the day would come when he’d be one of the people to nominate us for the prize.” It was Davisson who initially attracted Shockley to Bell Labs.
Brattain came very close, however, to not being around when the semiconductor research team was being put together. During the depression, he was next on a list of people to be let go if conditions got any worse, and later he had to convince his research vice president that he preferred research to supervising others.
One of the applications of the transistor that Dr. Brattain was most proud of was the development of the transistor radio. “This has made it possible for even the most underprivileged people to listen. Nomads in Asia, Indians in the Andes, and natives in
Haiti have these radios, and at night they can gather together and listen.” He added, “All peoples can now, within limits, listen to what they wish, independent of what dictatorial leaders might want them to hear.” He died when he was 85.
John Bardeen (1908-1987)
A brilliant theorist, Dr. Bardeen brought his keen understanding to the transistor team by explaining effects found in early transistor experiments.
Bardeen, born and raised in Madison, Wisconsin, obtained his Ph.D. in mathematics and physics from Princeton University in 1936. A staff member of the University of Minnesota, Minneapolis, from 1938 to 1941, he served as principal physicist at the US Naval Ordinance Laboratory in Washington, DC, during World War II, after which he joined Bell Telephone Laboratories, Inc. Bardeen stated that his, “introduction to semiconductors came just after the war, in late 1945, when I joined the Bell Laboratories research group on solid-state physics, which was being formed under the leadership of Stanley Morgan and William Shockley. Following a Ph.D. under Eugene Wigner at Princeton and post-doctoral years with John H. Van Vleck at Harvard, I had been interested in the theory of metals before the war and was anxious to go back to solid-state physics after five years at the Naval Ordnance Laboratory in Washington.” While at Harvard, Dr. Bardeen had become friends with James B. Fisk, who in 1945 was director of research at Bell Labs. Bardeen also knew Shockley when he was a graduate student at M.I.T. “It was they who persuaded me to join the group rather than return to my academic post at Minnesota. I was the first outsider to be recruited; the rest of the initial group had been at Bell Laboratories for some years.”
There he conducted research on the electron-conducting properties of semiconductors. This work led to the invention of the transistor.
“Conditions were rather crowded when I arrived at the Murray Hill, NJ, laboratory. The wind-up of World War II research was still going on.” He said a new building was under construction, so he was asked to share an office with Walter Brattain and Gerald Pearson. “I had known Walter since my graduate student days at Princeton. Although at that time I had not decided what field of solid-state physics I would work in, they soon got me interested in their problems and I became deeply engrossed in trying to learn what was known about semiconductor theory.”
Dr. Bardeen won the Nobel Prize in 1956 as co-inventor of the transistor, and again in 1972 as co-developer of the theory of superconductivity at low temperatures. Dr. Bardeen left Bell Labs in 1951 to join the faculty at University of Illinois, where he dedicated himself to research superconductivity. He died at age 78.
It was not just Bardeen, however, who won the Nobel Prize for Physics. Together with Bardeen were Shockley and Brattain, and some of their spouses and parents. In the end, all three won the recognition they deserved.
Toward the end of his career, Shockley became increasingly convinced that persons of African-American ancestry were inferior to white people in the area of intelligence. He coined the term “dysgenic” suggesting that blacks were inherently inferior and that only whites ought to be allowed to reproduce.
It is important to understand that Shockley had no education in the areas of genetics, biology psychology, or anthropology. Nonetheless, Shockley would attend meetings and would express these racist ideas. He would point out that US Army intelligence test scores of black recruits were lower than those of whites. Shockley appeared not to understand the methods of testing in place, or the limitations of intelligence testing. Some would argue that Shockley may have chosen to deliberately remain ignorant of such matters.
Today, we are aware that tests available at that time did not adequately account for cultural or economic disparities between black and white populations. Intelligence testing today is considered “colour-blind” in that separate tests are administered on the basis of cultural fairness. Further, psychometricians are aware that there is more to intelligence than “G” or, General Intelligence.
With adequate testing, there is no discernable difference between the scores of blacks and whites. It is unfortunate that Shockley took the position that black citizens ought to be paid to become sterile. Shockley would be jeered and booed by audiences he addressed on these matters. At the time of his death, Shockley looking back on his life ventured the opinion that his work in genetics was more meaningful than his work in semiconductor physics.
Pseudo-science occurs when an expert in one discipline trades on his credibility to make comments in disciplines he is totally unfamiliar with. Shockley certainly fit the bill in this regard. Modern psychologists consider that there is but one, unified and comprehensive human race. Anthropologists know that the so-called races are merely evidence of the fact that humans are incredibly adaptive and will alter their physical form, over time to conform to the environmental circumstances in which they develop.
Before we become too smug and congratulate ourselves for our progressive views, we need to consider that these sorts of problems continue to plague society today. In Europe, the fascist threat continues to build in such places as Austria, Germany and France. In North America we witness the continuity of white power formations such as the Ku Klux Klan, the Heritage Front, the Northern Alliance and other white supremist organizations. Even here in London, citizens are becoming increasingly concerned about the fact that white power groups are choosing this community to settle and do their business within. Even though he has been relegated to research and held away from students, a certain UWO psychologist continues to practice pseudo-science based on outmoded racist ideas.
Conclusions
I am fascinated by the history of science and technology. It is almost as interesting to understand how things came to be as it is to appreciate the manner in which aspects of technology actually function. I have attempted to convey in this presentation something of the drama of discovery and the affect that personalities can have on the development of new technologies. Please remember that the book “Crystal Fire” contains a great deal more information than I have presented this evening. It is full of basic physics and discusses the problems and challenges that the inventors had to confront.
If you are interested, read the book. You will not be disappointed. It is available in most branches of the London Public Library system.
Thank you.