SEMICONDUCTOR ARCHAEOLOGY.
or
TRIBUTE TO UNKNOWN PRECURSORS.
**************
In the beginning of the era of radio, listeners received transmissions on a crystal set.
This set consisted of an aerial, a tuned circuit, a detector and a earphone. (Figure 1.)
Fig 1. A classical crystal set..
The detector consisted of a anisotrope crystal of galena (lead sulphide), locked in a small cup.
One or several flexible metalic wires (cat whiskers) made contact on the cristal. These wires where made of
gold, brass, copper or steel ...This detector allowed an electric current to flow better in one way while jamming it
in the other. One spoke of "unilateral conductivity". This allowed the rectification of a high frequency
signal and the extracting of an audible or musical message.
The discovery of this rectifying property in certan crystals is credited to F. BRAUN in 1874.
In 1938 one was still not able to ascertain the manner in which this happened.
There was a great lack of knowledge in molecular physics and in solid material chemistry.
It was thought that some sort of thermo action took place or that it was also electrical.
In the years 1920-1922, a lot of home research about this function went on in Russia and the U.S.A.
But the evolution of radio electronics was to be swamped by the mighty and rapid progress made with
vacuum tube valves.This revolution made nearly every one forget the results and knowledge of the
early days.
It was only in 1945, that real research started up again resulting in the production of something that was
going to turn into today's semiconductors. Among these :
The invention of the point transistor by Bardeen, Brattain and Shockley. ( Nobel prize in 1956 )
The dicovery of the tunnel effect par Esaki. ( Nobel Prize in 1973 )
As to try and not totally forget all the work done on semiconductors before this recent period, we have
tempted to list the description of materials used and the accomplishments made between 1920-1938.
(This description has not got the pretention of being exhaustive.)
DETECTORS:
Three kinds :
- Contact between a crystal and a conductive pin.
- Contact (or junction) between two identical crystals.
- Contact (ou junction) between two non identical crystals.
These devices made up, what are called today as DIODES.
The electrical and mecanical performances of these diodes depended upon the pressure of the contact (or junction)
and of an eventual polarization voltage.
Examples of prehistorical characteristic curves are shown in Figure 2.
Fig 2.
I Contact Perikon (Zincite-Chalcopyrite)
II Contact Carborundum-Steel
III Contact Zincite-Steel
Zincite was made by using natural Zinc oxyde (ZnO) and heating it with an electrical arc in the presence of
manganese peroxyde or manganese bioxyde.
In our opinion, the most interesting device was made up by the contact between Zincite and Steel. (sometimes Carbon)
But the ancient characteristic curve in Figure 2 does not show it's most exciting aspect.
In 1923, someone managed to make a high frequency generator using such a detector.
But it was polarized. This indicates that this diode had a characteristic curve in which
a negative slope was present. And this makes one think of the tunnel effect diode invented a half a century
later.
In Figure 3, we have the characteristic curves of a normal diode and a tunnel diode where this
negative slope is visible.
Fig 3.
Tunnel Diode
The green curve has a negative slope between 200 and 300 mV.
Unknown precursors then took advantage of this discovery to build, way before out time, some semiconductor devices.
That is to say :
- heterodynes
- regenerative receivers
- low frequency modulators
- autodynes
- low frequency amplifiers
- high frequency generators(8 to 12 Mhz)
- transceivers...
These layouts where part of what one called CRYSTADYNE systems.
But in those days, the technical performance and industrial ease of the new increasing valve technology
made these layouts to be ignored, and then forgotten.
Here in the Figures 4 to 7 we show four original schematics of the "Crystadyne" technology.
They were printed before 1938.
Fig 4.
Zincite Heterodyne
Fig 5.
Crystadyne receiver.
Fig 6.
Zincite heterodyne for short waves.
Fig 7.
Zincite modulator. - Low frequency "tikker".
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