Ramón Escobedo's homepage
THE GUNN EFFECT
In 1963, J. B. Gunn reported that...
"When a pulsed electric field of several kV/cm is applied to a homogeneous
specimen of III-V semiconductor by means of "ohmic" contacts, an instability in
the current is observed. Under suitable circumstances this instability takes the
form of an oscillatory component superimposed upon the normal pulse current.
[...] The design and performance of a solid-state microwave oscillator [...] is
discussed. This oscillator permits the generation of useful amounts of microwave
power by a simple device which operates at room temperature without a magnetic
field, which contains no p-n junctions, has no inconveniently small dimensions, and which should be
cheap to manufacture.
"Recent work on the direct generation of microwaves in bulk semiconductors",
J. B. Gunn, Electron Devices Meeting (1963) p. 24.
Picture of J. B. Gunn: IEEE Trans. Elec. Dev. ED-23, 7 (July 1976) 786
Experimental observations of J. B. Gunn:Current oscillations... ...with a frequency of 4.5 Ghz... ... and a "noisy" I-V characteristic
In 1964, H. Kroemer, Nobel Prize in Physics (2000), proposed that...
"These semiconductors have a negative differential bulk conductivity above
the oscillation threshold field [...] The current oscillations are due to the periodic
nucleation and disappearance of traveling space-charge instability domains.
[...] As one high-field domain moves out of the crystal at the positive electrode
a new domain gets nucleated at or near the negative end. [...]
We wish to suggest that the origin of the negative differential mobility is Ridley
and Watkins' mechanism of electron transfer into the satellite valleys [...] in the conduction band.