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Radar During World War II


During World War II, battles were won by the side that was first to spot enemy airplanes, ships, or submarines. To give the Allies an edge, British and American scientists developed radar technology to "see" for hundreds of miles, even at night. The research that went into improving radar helped set the stage for post-war research into the transistor.

1940s radar relied on a semiconductor crystal, or "rectifier." Radar worked by sending out a radio wave and analyzing the reflected wave after it bounced off any objects in the air. The rectifier's job was to translate the reflected signal into the direct current necessary for visualization on the screen. These crystals often couldn't handle the quickness and intensity of a rapidly changing radar signal. They would burn out frequently. A number of institutions, including Purdue, Bell Labs, MIT, and the University of Chicago, joined forces to build better crystals.

Trying different semiconductors and doping with different materials, the researchers learned which combinations produced the best results. Of special importance to semiconductor researchers was Seymour Benzer's discovery at Purdue. He found that germanium crystals made the best detectors. (Germanium was used to make the first working transistor five years later.) Scientists also learned new techniques on how best to grow and dope the crystals.

Within the decade, this superb understanding of crystal growing would pay off in unexpected areas, not the least of which were the insights necessary to allow the solid state researchers at Bell Labs to grow the germanium semiconductors that were the heart of the first transistors.

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