Transistor Invention & History - when was the transistor invented

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It was just before Christmas, on the 23rd December 1947 when the team of Shockley, Bardeen and Brattain demonstrated their new invention of a point contact transistor to senior management at Bell Laboratories in the USA.

Nobody could have envisaged the major impact that the invention of the transistor would have on the electronics industry and in fact the whole world. It had been just a week since the team had first successfully managed to get the device to work. Thus the date for the invention of the transistor could be said to be 16th December 1947.

The invention of the first transistor was a story of determination amidst a number of setbacks; a story of perseverance and ultimate success.

It is also a reminder, that although Shockley, Bardeen and Brattain are the names associated with the invention of the transistor, there were many people who supported them and many others who had set the foundations in place for the invention of the point contact transistor.

Transistor history foundations

There were many foundations that needed to be set in place before the invention of the transistor could be made.

People had been familiar with Ohmic conductors for many years and understood how basic resistors operated, but there was a class of materials called semiconductors that were slightly different. Even in the nineteenth century it had been observed that these semiconductors had a negative coefficient of resistivity, they were able to rectify electrical currents and they exhibited a photoelectric effect.

An early application of semiconductors was with wireless sets where cat's whisker or crystal detectors were used.

Later in the Second World War some more foundations were set in place as coper oxide and selenium rectifiers started to be used for rectifying AC power.

Also work on point contact diodes enabled microwave signals to be detected or demodulated for the radar sets that were using ever higher frequencies.

A further foundation that was set in place for the invention of the transistor in the 1920s and 1930s, was theoretical work on the sub-molecular physics. Although this was initially directed towards thermionic devices, i.e. vacuum tubes or valves, it had a huge impact on the understanding of semiconductors.

Early transistor related findings and patents

The first patent that was recorded for work on the transistor was filed by an Austrian-Hungarian physicist named Julius Lilienfeld on 22nd October 1925 in Canada. But, as he did not make any research publications regarding the invention of the transistor, the industry ignored his work. However his work defined what we now call a field effect transistor and this was what the team that ultimately started working on he transistor were aiming to make.

Later, in 1934, a German physicist named Oscar Heil filed his patent for a device that controlled the current in a circuit by applying an electric field - effectively a field effect transistor. Although not a bipolar device, it was what the first team at Bell started investigating. As for Heil, he did not submit any real findings and his ideas were only theoretical and as a result his work was not noted in the scientific community.

Transistor work starts at Bell

As hostilities started to draw to a close, Bell Laboratories realised that there were major possibilities for semiconductor technology. In the spring of 1945 a major meeting was called to discuss the future research into them - this was a pivotal point in the transistor history. Later that year authorisation was granted for research to proceed to seek "new knowledge that could be used in the development of completely new and improved components".

As a result a solid state physics group was set up under William Shockley and Stanley Morgan. Shockley also headed up the semiconductor sub-group which was to include Brattain and Bardeen to make up the trio who invented the transistor.

Transistor trio

The three main characters involved in the transistor history were:

• William Shockley:  

  Note on William Shockley:

  He was born in London in 1910 of American parents, but they returned to the USA after three years, settling near San Francisco. He gained his first degree from the California Institute of Technology after which he moved to the Massachussetts Institute of Technology to gain his Ph.D. in 1936. After graduating he moved to Bell Labs where he lead the team that invented the first transistor. In his life he went on to invent other devices and set up his own company.

  Read more about William Shockley.

• Walter Brattain:  

  Note on Walter Brattain:

  He was born in China, moving to Washington State when his parents returned home. He took his first degree at Whitman College in Washington State, moving to the University of Minnesota to gain his Ph.D.. After university, Brattain initially worked for the National Bureau of Standards before moving to Bell Labs where he was one of the tree men who are credited with inventing the first transistor.

  Read more about Walter Brattain.

• John Bardeen:  

  Note on John Bardeen:

  He was born in Wisconsin in May 1908, taking his first degree at the University of Wisconsin, then moving to Princeton for his Ph.D.. After a couple of teaching posts he joined the solid state physics group at Bell Laboratories in the Autumn of 1945 where he was one of the trio who invented the first transistor. He was awarded two Nobel prizes in his life, one for work on the transistor, the other for work on superconductors.

  Read more about Georg Ohm.

With the preparatory work done, and the team assembled, the transistor history moves onto the actual invention of the transistor.

It took many years for all the preparatory work to be set in place and the team to be set up before the actual transistor invention or transistor discovery could be made.

The team that invented the transistor worked well together, and despite some initial set-backs they made quick progress.

The environment that Bell Labs had set up worked well and this provided the right atmosphere for the transistor invention.

First attempts at the transistor invention

The semiconductor group started work on one of Shockley's ideas. He had deduced that it might be possible to develop a form of semiconductor triode. He envisaged a structure of layers of p and n type silicon. The main current would be carried in one of the layers and the conductance of this layer would be controlled by an external field. This would vary the number of charge carriers (holes or electrons) available to carry the current. Essentially this idea was the field effect transistor which is in widespread use today.

To create the structure to try out this idea, Shockley used some thin films of silicon which had been made by deposition. This in itself was a new process which had only just been developed by another Bell employee named Teal.

Using the new structure, Shockley expected that there would be a significant change in conduction as the controlling field was altered. To his great disappointment the effect was not observed. Calculations and theories were checked and rechecked by other members of the group and no reason was found for its failure.

It was not until March 1946 that the problem was solved. Bardeen reasoned that the semiconductor surface trapped electrons which screened the main channel from the effects of the external field. Later Shockley said that this discovery was one of the most significant developments in the whole of the semiconductor programme.

Change of Direction

Supposedly beaten by the trapped electrons the group changed direction. They turned their attention to investigations around reversed biassed PN junctions in an attempt to develop a new kind of lightning arrestor. Research revolved around three layer structures with one forward and one reverse biassed junction, and work progressed on this through most of 1947.

It was towards the end of that year that events started to look up for the group. In November a new recruit to the team came up with a crucial idea. Returning to their earlier work on field effect devices he suggested that if an electrolyte was placed between the control plate and the conduction channel then the screening effect of the trapped electrons might be overcome. A new experiment was set up and it was successful, if only to a limited degree. With a measure of success behind them the team found a new degree of motivation. In the days that followed a host of ideas for possible amplifying devices were discussed.

Transistor invention

In early December, Bardeen and Brattain started to experiment with two closely spaced point contact junctions as a new idea for the transistor invention. They found that when they forward biassed one and reverse biassed the other, a small amount of gain was noticed.

Soon the team started some further experiments based around this idea, but initially they were not able to exploit the transistor effect properly. In one experiment an electrolyte was even placed around the sample, but with each new test they came a step closer to discovering the full transistor effect.

Finally they decided that it was necessary to place two diode junctions about 0.05 mm apart. Initially the idea seemed impossible as it was not feasible to place two wire point contacts so close together.

However the solution was achieved remarkably easily. A layer of gold was deposited onto a small wedge of perspex. Then a razor blade was used to cut a very thin slit in the gold right at the point of the wedge. Then the wedge was placed onto a layer of germanium under the force produced by a small spring. The collector and emitter were formed by the two gold contacts and the germanium layer was the base contact.

The idea was tried on 16th December 1947 and to their surprise it worked first time. The first point contact transistor had been made and the first transistor had been invented.

The invention of the transistor heralded the beginning of the transistor age. However many more developments were needed before these devices could become an everyday reality.

Official announcement of transistor invention

Although there was great excitement about the invention of the transistor, it was not until 30th June 1948 that Bell Labs publicly announced the new device, which John Pierce named a transistor.

The name transistor came about as it is a combination of the words "transconductance" or "transfer", and "varistor". The varistor element of the word was used because the device logically belongs in the varistor family, and it has the transconductance or transfer impedance of a device having gain.

In the announcement by Bell Labs, it said that the transistor invention "may have far-reaching significance in electronics and electrical communication."

The device was also patented, and interestingly Bardeen and Brattain and not Shockley were named on it.

Parallel transistor invention

Like many other inventions in history, there was other similar work being undertaken in other parts of the globe, and a point contact transistor was invented at very much the same time in France.

Two German physicistsIn 1948, Herbert Mataré and Heinrich Welker had been heavily involved with the German radar work in World War II working at the Telefunken laboratories. Matare worked primarily in Berlin, while Welker was based in Munich.

As part of this work, Matare had been investigating crystal rectifiers made out of both germanium and silicon, and Welker had been working on methods for purifying germanium.

After the end of the war, both were employed at a Westinghouse subsidiary called Compagnie des Freins et Signaux. Their aim was to develop and manufacture solid state rectifiers.

In 1947, just as work was progressing in the USA, Matare was researching a phenomenon where two very closely spaced point contacts could interfere or influence each other - something which he had seen during the war.

Early in 1948 Matare had been able to achieve results where he saw some amplification on occasions. By mid-1948, work by Welker to produce crystals with a much higher level of purity enabled much better results. to be obtained.

Just after they managed to complete their work and obtain reliable operation of these new devices they learned of the transistor invention at Bell Labs in the USA.

In view of this news from the USA, the "transistor" invented in France was rushed into production and named a "transitron." Production of these devices was soon ramped up and they were widely used within the French telephone system.

After the first transistors had been demonstrated, and announced, it was the Bell Laboratories device that became the defacto first transistor, but looking at the performance of both devices it was obvious that much more work was needed to enable transistor technology to become a mainline device for the electronics industry.

The invention of the first transistor was only the first step along the road to the semiconductor technology which we all enjoy today.

  Written by Ian Poole .
  Experienced electronics engineer and author.

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