Negative Resistance Arising from Transit Time in Semiconductor Diodes

Copyright, 1964, American Telephone and Telegraph Company Negative Resistance Arising from Transit Time in Semiconductor Diodes By W. SHOCKLEY (Manuscript received J a n u a r y 22, 1954) The structural simplicity of two-terminal compared to three-terminal devices indicates the potential importance of two terminal devices employing semiconductors and having negative resistance at frequencies properly related to the transit time of carriers through them. Such negative resistances may be combined with un symmetrically transmitting components, such as gyrators or Hall effect plates, to form dissected amplifiers that may be made to simulate conventional three-terminal amplifiers and operate at high frequencies. The characteristics of several structures are analyzed on the basis of theory and it is found that negative resistances are possible for properly designed structures. 1. NEGATIVE RESISTANCE AND DISSECTED AMPLIFIERS Because the drift velocities of current carriers in semiconductors are smaller than the velocities attainable in vacuum tubes, transistor structures must be smaller to achieve comparable frequencies. In principle it is possible, of course, to make compositional structures (i.e., distributions of donors and acceptors) in semiconductor crystals on a scale much smaller than is possible for vacuum tubes. At present, however, the available techniques are limited and it may require many years before the ultimate potentialities are approached. 799 800 THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1954 It is instructive, however, to speculate on some of these ultimate potentialities.