Walter Schottky was one of the first researches to study the vacancies
in the structure of the semi-conductor materials.
|Fig. 252 - The barrier diode invented
by Dr. Schottky.
In reality they are holes in the crystal lattice due to the movement
of electrical charges.
|| Fig. 253 - The four-element
Thyratron valve provided with shield grid where:
c) Control grid
d) Shield grid
Such a kind of strucuture was known later as the "Schottky
defect". These studies led him to postulate 1938 a theory that
explained the rectifying behaviour of a metal-semiconducting contact
as dependent on a barrier layer at the surface of contact between
the two materials. The metal-semiconductor diodes later built based
in this theory is known as Schottky barrier diodes.
Basically this type of diode has a metal-semiconductor contact such
as an Aluminum layer in intimate contact with an N-type Silicon
substrate. Thus the diode behaves electrically similar to a P-N
junction, in such way the current flow is caused originally to majority
carriers having an inherently fast response.
The barrier diode is used in several kinds of circuit topology such
as: low noise mixers, microwave or high frequency as well as comutators.
In the path of its technological development soon led to a new type
of diode, whose operation principle was similar to a gaseous triode
valve as known as the Thyratron. Fig 253