Page 32 - A Practical Guide from Design Planning to Manufacturing

8 Chapter One

could vary the resistance between emitter and collector, it was later
decided to call the device a transfer-resistor or transistor.
It was immediately apparent that the transistor would be an
extremely important innovation and Bell Labs began the process of
applying for a patent immediately. Shockley felt that Bardeen and
Brattain’s success had come as a result of his field-effect concept and that
Bell Labs should file a broad patent to include his field-effect ideas and
the newly created transistor. Furthermore, as leader of the team,
Shockley felt that his name alone should appear on the patent.
Shockley’s harmonious research team quickly became polarized over
the question of who should receive credit for the new invention. Bell Lab
attorneys might have given Shockley what he wanted, but in reviewing
the patents already on record they found something disturbing.
An obscure physics professor named Julius Lilienfeld had been
granted two patents in 1930 and 1933 for the idea of controlling the cur-
rent in a semiconductor by means of an electric field. Although there was
no record of Lilienfeld ever trying to build his device and surface charges
would almost certainly have prevented it from working if he did, the idea
was clearly the same as Shockley’s. A patent on a field-effect transistor
would almost certainly be overturned. The attorneys at Bell Labs
decided to write a more narrow patent application focusing just on
Bardeen and Brattian’s point-contact transistor, which worked on dif-
ferent principles. Ultimately patent 2524035, “Three-Electrode Circuit
Element Utilizing Semiconductive Materials” lists only Bardeen and
Brattain as inventors.
Shockley felt he had been robbed of proper credit and began working
on his own to devise a new and better transistor. The point-contact tran-
sistor shared all the same problems as cat whisker diodes. Because it
required two metal lines to just touch the surface of the semiconductor
it was extremely temperamental and hard to consistently reproduce.
Shockley reasoned that if a transistor could be formed out of two cat
whisker diodes sharing one terminal, perhaps he could make a transistor
out of two junction diodes sharing one terminal.
He began working out the theory of a junction transistor but told no one
at Bell Labs until February 1948, when experiments with the point-contact
transistor suggested that charge carriers could travel through the bulk
of semiconductors and not just at the surface as Bardeen and Brattain
had been assuming. Knowing this was proof that his concept for a
transistor could work, Shockley now described his ideas to the group.
It was obvious to Bardeen and Brattain that Shockley had been thinking
about this for some time and intentionally kept them in the dark. In June
1948, despite not yet having a working prototype, Bell Labs applied for
a patent of the junction transistor listing only Shockley’s name. Bardeen
and Brattain would never work effectively with Shockley again.