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Your Engineering Heritage
Twists
and Turns in the Development of the Transistor
by
John Vardalas
Invented at Bell Telephone Laboratories between
1945 and 1948, many consider the transistor to be one of the most important inventions in 20th
century technology. The story of the first working transistor
underscores the power modern industrial laboratories have had to
coordinate scientific discovery in the pursuit of technological
breakthroughs. It is about great intellectual leaps and driving
ambition. But while the story has been told and retold to
scientists and engineers for years, only a small circle of history
buffs and scholars know that the pursuit of the solid-state
amplifier has an even longer history than the transistor. This
quest dates back to 1924–1925, and the work of Julius Edgar
Lilienfeld.
The Dawn of
the Electronics Age
Though Karl
Braun’s cathode ray tube (1897) and Ambrose Fleming’s vacuum
tube rectifier (1904) marked the beginning of the electronics age,
Lee de Forest’s triode actually propelled electronics forward.
By placing a wire “grid” between the cathode and anode, de
Forest transformed Fleming’s rectifier into an amplifier. With
amplification, radio communications blossomed and long-distance
telephony became a reality.
The very success
of the triode, however, brought out its long-term limitations. It
was a fragile device that consumed a lot of power. And so in the
mid-1920s, with an eye on radio technology, Julius Edgar
Lilienfeld set out to find a solid-state replacement for the
thermionic triode.
Lilienfeld
Follows His Intuition
In patent
applications to Canada in 1925 and to the United States in 1926,
Lilienfeld claimed that his solid-state amplifier “relates to a
method of and apparatus for controlling the flow of an electrical
current between two terminals of an electrically conducting solid
by establishing a third potential between said terminals.” He
filed two more U.S. patent applications in 1928. In his 28 March
U.S. patent application, Lilienfeld was more explicit about what
he was after: “the provision of a simple, compact and
substantial device which withal shall be inexpensive to construct.”
Offering an alternative to thermionic principles, Lilienfeld
argued that his novel device “[could] be operated under much
lower voltage conditions than heretofore.”
No one really
knows whether Lilienfeld ever tried to build his device. Even if
he did, the device would not have worked well, if at all, since
the production of high-quality semiconductor materials was still
decades away. Thus, in the 1920s and 1930s, Lilienfeld’s
solid-state amplifier ideas had no practical value to the radio
industry.
Like so many
patents, Lilienfeld’s went into obscurity. Nevertheless, his
ideas embody the principles of the modern-day, field-effect
transistor (FET).
History is
Sketchy
Little is known
of the intellectual journey that led Lilienfeld to his
field-effect approach to solid-state amplification. Even the
details of his life are sketchy. Like so many pioneers in
solid-state electronics, Lilienfeld was an accomplished physicist.
Born in Poland in 1881, he obtained his Ph.D. in 1905 at the
University of Berlin. In 1910, he became a physics professor at
the University of Leipzig. His early interests seem to have
focused on cryogenics.
In 1911,
Lilienfeld filed a U.S. patent for separating gas mixtures. He
also worked with Count Ferdinand von Zeppelin on designing
hydrogen-filled dirigibles. From 1914 through the early 1920s,
Lilienfeld made important contributions to x-ray tube design,
receiving six U.S. patents. In 1927, Lilienfeld left Germany to
escape the rising tide of anti-Semitism, immigrating to the
United States. Here, while head of an industrial research
laboratory, he patented several contributions to capacitor
technology, including the first solid-state electrolytic
capacitor. It could be that work on capacitors led him to conceive
of the solid-state amplifier through the framework of electric
field effects.
From the
Grave to the Forefront
For nearly two
decades, Lilienfeld’s field-effect approach lay buried and
forgotten. Then, in 1947, it reached out from the grave to shape
Bell Telephone Laboratories’ (BTL) patent strategy on the
transistor. In the process, it frustrated William Shockley’s
grand ambition. Although the vacuum tube had made long distance
telephony possible, Bell Telephone was keenly aware of the tube’s
limitations. In the late 1930s, Shockley began looking for a
solid-state version of the triode, but with little success. At the
end of World War II, he was in charge of a group pursuing a solid
state-amplifying device.
Shockley now
focused his attention on using an electric field as the “valve”
to control the flow of electrons through a semiconductor. His
theoretical analysis convinced him and others that it should work.
Shockley’s solid-state group, which included John Bardeen and
Walter Brattain, struggled to turn the field-effect, semiconductor
amplifier into a working prototype, but they failed. Along the
way, Bardeen and Brattain developed new theoretical insights and a
different design — the point-contact transistor or “bipolar
transistor,” as it became known.
The moment
Bardeen and Brattain had proven the
point-contact transistor to Bell senior
management, BTL drew up a
patent application. Then, out of the blue, Shockley summoned
Bardeen and Brattain separately to his office.
According to
Lillian Hoddeson and Vicki Daitch, authors of a recent biography
of John Bardeen, Shockley informed each of them individually “that
he could write a patent — starting with the field effect —
on the whole thing,” adding that “sometimes the people who do
the work don’t get the credit for it.” Bardeen and Brattain
were stunned. Shockley believed that the first BTL patent for a
solid-state amplifier should be based on the conceptual model of
the field-effect that he had developed and that he should be named
the inventor. BTL lawyers balked at Shockley’s request, having
unearthed Julius Edgar Lilienfeld’s patents. The idea of using
an electric field as a “grid” was not new. Shockley had not
been the first to suggest using a field-effect approach. However,
in Bardeen and Brattain’s prototype it was the “holes” that
acted as a kind of grid, and that was new. So BTL’s first patent
went with the point-contact transistor.
Lilienfeld’s
Work Dominates Modern Electronics
The events that followed Bardeen
and Brattain’s invention of the bipolar, point-contact
transistor took many
unexpected twists and turns. Shockley did not put all his eggs in the field-effect
basket. Not to be outdone by Bardeen and Brattain, Shockley
secretly worked on a different bipolar device. Within a short
time, his patent for the bipolar junction transistor had wiped out
all commercial interest in the point-contact transistor. Shockley
remained committed to the value of his field-effect theory, but
was unable to make a go of it. More than 15 years of material
technology advances would be needed before the first practical FET
appeared. Today, 75 years after Lilienfeld’s work, Metal-Oxide
Silicon (MOS)
transistors, which are built around field-effect principles,
dominate semiconductor electronics.
Lilienfield
Acknowledged As Pioneer
In an address to
the American Institute of Physics in 1988, Bardeen acknowledged
the great credit due Lilienfeld for his pioneering efforts to make
the semiconductor amplifier. In the 1920s, Lilienfeld could not
have understood the physics of the field-effect semiconductor
amplifier, as the quantum theory of solids was still several years
away. Nevertheless, he had a good intuitive feel for a new
approach to electronics. In Bardeen’s own words, “Lilienfeld
had the basic concept of controlling the flow of current in a
semiconductor to make an amplifying device. It took many years of theory
development and material technology to make his dream a
reality.”
John
Vardalas is an IEEE Postdoctoral Fellow in the Department of History, at Rutgers University in New Brunswick, N.J. Visit the IEEE History
Center's Web page at:
www.ieee.org/organizations/history_center/
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