1948 - Conception of the Junction Transistor

William Shockley conceives an improved transistor structure based on a theoretical understanding of the p-n junction effect.

After Bardeen and Brattain's December 1947 invention of the point-contact transistor (1947 Milestone), Bell Labs physicist William Shockley began a month of intense theoretical activity. On January 23, 1948 he conceived a distinctly different transistor based on the p-n junction discovered by Russell Ohl in 1940.(1940 Milestone) Partly spurred by professional jealousy, as he resented not being involved with the point-contact discovery, Shockley also recognized that its delicate mechanical configuration would be difficult to manufacture in high volume with sufficient reliability.
Shockley also disagreed with Bardeen's explanation of how their transistor worked. He claimed that positively charged holes could also penetrate through the bulk germanium material - not only trickle along a surface layer. Called "minority carrier injection," this phenomenon was crucial to operation of his junction transistor, a three-layer sandwich of n-type and p-type semiconductors separated by p-n junctions. This is how all "bipolar" junction transistors work today.
On February 16, 1948, physicist John Shive achieved transistor action in a sliver of germanium with point contacts on opposite sides, not next to each other, demonstrating that holes were indeed flowing through the germanium. Shockley applied for a patent on the junction transistor that June and published his detailed theory of its operation in 1949. Still, it was two more years before Bell Labs scientists and engineers developed processes that allowed his junction transistor to be manufactured in production quantities (1951 Milestone).

William Shockley describing junction transistor theory

Ricardo A monroy B
C.i 17646658
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