October 1959 Electronics World
Table of Contents
Wax nostalgic about and learn from the history of early electronics. See articles
Electronics World, published May 1959
- December 1971. All copyrights hereby acknowledged.
Tunnel diodes came onto the
commercial, military, and aerospace scene in the late 1950s. Exploiting the
phenomenon of quantum-mechanical tunneling, the device exhibits a negative resistance
region which makes it suitable for amplifier and oscillator applications. It also
permits operation into the tens of gigahertz realm, which was new ground at the time.
X-band and above was the exclusive realm of laboratory-based experiments using
klystrons and exotic chemical oscillators (pseudo-maser - microwave amplification by
stimulated emission of radiation). Tunnel diodes quickly became a part of
miniaturized radar units, battery-powered communications systems, undercover (spy)
operations, and many other applications.
"Tunnel Diodes" - Experimental Semiconductors
Insensitive to temperature changes and 100 times
faster than today's transistors, these devices bear watching.
Dr. Guy Suits, G-E vice-president and director of research, speaks
into microphone, while Dr. Jerome Tiemann holds the transmitter. In foreground, ordinary
FM receiver picks up signal.
Nestled inside a paper clip, a tunnel diode is shown in close-up view.
Connecting wire leads to alloy soldered to germanium crystal which is soldered to metal
Vest-pocket transmitter, making use of a tunnel diode, and with a
range of about one-half mile, is demonstrated by G-E scientists.
The newest "baby" in the fast-growing family of semiconductor devices - the "tunnel
diode" - is coming of age. The new device, first reported in 1958 by Japanese scientist
Leo Esaki, is closer to commercial application as a result of intensive research programs
at G-E and other companies. The special diode is a heavily doped junction semiconductor
that has a negative-resistance characteristic over part of its operating range (see the
The tunnel diode takes its name from the physical phenomenon that makes it possible:
"quantum-mechanical tunneling." The term is used to describe the manner in which the
electrical charges move through the device. Such motion takes place with the speed of
light, in contrast to the relatively slow motion of electrical charge carriers in transistors.
These high speeds make it possible for the device to operate at extremely high frequencies.
Oscillation higher than 2000 mc. has already been obtained and frequencies of more than
10,000 mc. are expected in the near future.
This high-speed response also- suggests applications in computers. When used as switches,
tunnel diodes have functioned in a fraction of a millimicrosecond - from 10 to 100 times
faster than the fastest transistor now available.
A complete tunnel diode transmitter is compared in size with a 50-cent piece. The
transmitter consists of one variable and two fixed ceramic capacitors, a coil that tunes
to the operating frequency - which may be higher than 2000 mc. - and the diode itself,
located inside the "can" in the center of the device. Battery is not shown.
The device also resists the damaging effects of nuclear radiation. Because it is less
dependent on the structural perfection of its crystal than is the transistor, it is much
less affected by the damage that radiation can do to such crystal structures. In this
respect it outranks transistors by more than 1000 to 1. Materials used for tunnel diodes
include silicon, germanium, gallium arsenide, gallium antimonide, and indium antimonide.
Silicon tunnel diodes work at temperatures 250°F higher than temperatures at which
conventional silicon diodes and transistors operate.
The negative-resistance characteristic allows the unit to be used as an amplifier,
a generator of r.f. power, and a switching device. Its simplicity makes possible the
development of integrated circuits. It is superior to vacuum tubes and transistors for
applications in low-noise amplifiers and mixers for high frequencies. Many parametric
amplifier jobs, for example, could be performed more easily with tunnel diodes.
G-E now has plans to offer limited quantities of experimental samples in the next
Posted August 8, 2018