Vacuum Tubes


Quantum Mechanics




The Point Contact

The P-N Junction

The Junction
(sandwich) Transistor

The First
Silicon Transistor

Modern Transistors

The Four Layer Diode

The Chip

Recreating the First

Germanium Comes of Age


Semiconductors had been discovered in the early 1930s, but not much was known about them. While scientists weren't sure how they worked, they were certain that semiconductors were useful.  Semiconductor crystals were used in radio and radar receivers because they could take in the high-frequency alternating signal of the radio wave and extract the low frequencies necessary for the headphones. Crystals which did this were known as rectifiers. 

During World War II, radio and radar were extremely important -- and therefore so were rectifiers. But rectifiers had a problem known as "burn out."  Sudden bursts of electricity in the wrong direction could destroy them.  So one of the tasks the US government gave scientists during the war was to produce better rectifiers. 

It was the Purdue University Physics lab, led by Karl Lark-Horovitz, that managed to make them. One of the graduate students, Seymour Benzer, accidentally discovered that a crystal of germanium -- a semiconductor which was not well understood at the time -- could withstand higher voltage than any current rectifier.  Benzer spent over a year tinkering with germanium until he discovered that mixing in trace elements of tin could produce rectifiers that were ten times more resistant than was standard. 

Most people who heard about the results wouldn't believe it until they saw it with their own eyes.  But soon germanium was established as a crucial part of semiconductor research. 

-- Karl Lark-Horovitz 
-- "The Origin of Semiconductor Research at Purdue: A Glance at the Past by One of the Early Participants" by Ralph Bray 
-- "A History of Physics at Purdue: The First Phase of the Lark-Horovitz Era, 1928-1942" by Solomon Gartenhaus, Arnold Tubis, and David Cassidy 
-- "Solid State Physics Research at Purdue" by Paul W. Henriksen.  Osiris, 1987. 
-- Crystal Fire by Michael Riordan and Lillian Hoddeson 

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