Is there a light at the end of the tunnel?
(The Tunnel-Diode, that is)
At the dawn of the electronic solid-state era, basic devices were fabricated as discrete components and underwent quality-control testing individually. The diode was one of these devices. It was so named because it is composed of two slabs of silicon crystals tightly sandwiched together. The two slabs are "doped" with different elements during crystal manufacturing, which gives them opposite internal electrical charge permanently. The one with the positive charge is named "p-type", and the other is named "n-type" accordingly. When sandwiched together, they create a permanent static electrical field internally. This device is primarily used to convert alternating-current into direct-current by allowing the current to flow only in one direction and completely blocking it from flowing in the other direction. It can do this due to the internal static electrical field. It is termed a "rectifier" in this function.
When subjected to testing, it displayed a smooth curve and passed the test. However, some devices exhibited a flaw in their curve. Such a unit was thought to have become contaminated during manufacturing and was routinely discarded until an astute testing-engineer named Esaki realized that if such a "faulty" device operates at the point of the "flaw", it would exhibit the characteristics of an amplifier. Thus, a "tunnel-diode" was born. This name was derived from the explanation of its function by applying the theory of "tunneling". It was accomplished by invoking the quantum physics phenomena such as: "wave-particle duality" the "uncertainty-principle" and "entanglement".
As it turned out, it was accidentally overdoped during the production process, which resulted in a much stronger internal electrical field. This caused it to abruptly reach saturation during the test procedure and display a distorted curve. It's similar to a common practice of having magnetic components deliberately made to saturate in order to achieve a desired outcome in certain electronic circuits.
The current flowing through a regular diode increases with an increased voltage across it resulting in a display of a smooth curve. However, in an overdoped diode increasesed voltage deepen the device saturation which causes the current to decrease instead. This displays a curve which is bent backward on itself and is known as "negative-resistance"—a typical characteristic of an amplification device.
The conclusion is that a tunnel-diode is nothing but a heavily doped diode that operates as an amplifier in its saturation region.
P.S.
A Word about Tunneling
The theory of tunneling proposes a momentarily existence of wormhole in space-time continuum which can let thorough a single particle to time-travel. But this particle has the unique ability to naturally travel in time anyway. It does that without a wormhole by the virtue of being an unattached single particle. Moreover, it moves continuously—not just momentarily—as described in
"It's About Time".
It appears that there is no light at the end of an unexciting tunnel.
I apologize for demystifying yet another myth of quantum physics and for proposing a simple (
simplistic, you say?
*)
explanation of some of its elements while being well aware of the gurus of this field asserting that quantum physics is not meant to be understood.
*
For more "elaborate" treatments, you would be better off looking elsewhere.
I am afraid there are none of these on this site. Sorry.
Joel Tepper, P.Eng.
telejt[delete_me]@shaw.ca
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