The Story Behind the Invention of Field Effect Transistors

john December 10, 2013 3 Comments

No one can certainly imagine any electronic device without the presence of transistors. In that case, what was the idea behind the invention of transistors? Who were the people behind its invention and advancements? What was the real purpose behind the invention of field effect transistors? And how did it emerge? What are the current applications and advancements of these transistors? Have you ever wondered about these? If yes, then this write up will help you in knowing more about the interesting story behind the invention of the field effect transistors.

Before entering into its invention part, let us have a brief look on what field effect transistors are. Field effect transistors are unipolar transistors which basically emerged from the bipolar transistors. It is employed as a transistor but its efficiency is that it controls the conductivity of the material with the help of an electric field.

Though there are too many people involved in this invention, a few are noteworthy. Julius Edgar Lilienfeld, Oskar Heil, John Bardeen, Walter Houser Brattain and William Shockley have made major contributions towards the invention of the field effect transistor.

The Invention

Until the beginning of the 1900s, in fact, there was no idea about the principle that led to field effect transistor.

Two people have patented their ideas on this invention.

Contributions of Julius Edgar Lilienfield

Julius Edgar Lilienfeld

Julius Edgar Lilienfeld

The first person is Julius Edgar Lilienfeld who was an Austro-Hungarian physicist. He later moved to the United States and became a US citizen. In 1905, he started working in the University of Leipzig in the Department of Physics.

His work interest was on the discharge of electrical particles or electrons in a vacuum. His first contribution towards the scientific society was made with the identification of the field electron emission.

He was the one to invent the field effect transistor or FET as it is commonly known. His other inventions include the electrolytic capacitor which was invented in the same period of 1920. He claimed patents for various works among which he was granted a patent for the FET of field effect transistor on January 28, 1930.

Based on one of his discoveries that was similar to the X-ray tubes, any optical radiation emitted by the hitting of electron on a metallic surface was termed as Lilienfeld radiation.

Oskar Heil and his Contributions

Oskar Heil

Oskar Heil

Unlike Lilienfeld, Oskar Heil was an electrical engineer. He finished his studies at the George-August University. A doctorate was awarded to him for his work on Molecular spectroscopy in 1933.

Based on the reports of various patents issued to him, Oskar Heil is found to be one of the inventors of the field effect transistors. The other inventions that are recorded by him are Air motion transformer and Heil tube.

In the year of 1963, after gaining a lot of experience, he initiated his company in California, USA.

Contributions of William Shockley

Though the principle of field effect transistors was first patented by Lilienfeld and Heil, the practical semi-conducting devices such as the junction gate field effect transistor or JFET were developed years later after the transistor effect was observed, explained and demonstrated by William Shockley and his team at Bell Labs in the year 1947.

Shockley’s effort on commercializing the transistor was a path breaking contribution in the scientific society. During the Second World War, Shockley was working in the radar research laboratories at the New Jersey. The first working transistor was built by Shockley. It was a germanium point transistor of A series.

The transistors that are currently employed in electrical devices are all, MOSFETS. MOSFETS are Metal oxide semiconductor field effect transistors. These were first proposed by Dawon Kahng in 1960 and this transistor largely superseded the JFET and had a much more profound effect on electronic development.

How the Field Effect Transistor Works

In the field effect transistor, an electric field is created by a weak electric signal at the bottom of the transistor which is further passed to the other parts of the field effect transistor.

The bottom of the transistor is filled up with excess of electrons.  In the central or the base region, the count of the electrons is too less when compared to the bottom part of the semi conductor. There are two sides found, that are known as the source and the drain. The source side is the region form where the electrons enter inside and similarly on the other region, drain, the electrons drains out. Normally the flow of electrons is made from one side to the other. The flow of current is not marked close to the base region. The flow of current is facilitated by a thin channel along the other region.

To the base of the semi conductor, an electrode is linked or attached. A thin layer of metal oxide separates this electrode from the rest part. Most common heavy metal oxide used is the silicon dioxide. The electrode is often addressed as ‘the gate’. The gate is where we pass the weak electrical signal into the semi conductor.

Due to the repulsive action of the electrons, a depletion zone gets formed at the base region. Passing negative charge will help in completely preventing the passage of electricity through the semi conductor.

Though transistors have varied applications that are simpler, they can be employed in complex places too. They can also behave as amplifying devices.

Based on the charge passed on to the semi conductor, the current flowing through the other region can be either smaller or larger. As there is another voltage connected to it, there are possible ways to further make it larger. The field effect transistors or FET are commonly employed in electrical devices such as microphones, micro wave ovens, televisions, radios and even in automobiles. They have a wide application as charge carrier devices. Though there are many other semi conductors available, silicon serves the best to be used in field effect transistors.

Comments
  • please more explanations about the field effect action,,,take from the history space and expand in explanation,,,,with drawings

  • mahesh
    January 28, 2014

    fet experiment

  • mahesh
    January 28, 2014

    fet

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