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Shockley's notebook





The Sandwich Transistor

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Shockley Invents the Junction Transistor

January and February, 1948

A Solitary New Year's Eve

William Shockley spent New Year's Eve alone in a hotel in Chicago. He was there for a Physical Society meeting, but he was most excited about having some time to himself to concentrate on his work. There may have been a party going on downstairs, but Shockley wanted nothing to do with it. He had more important things to think about. He spent that night and the next two days working on some of his ideas for a new transistor-one that would improve on Bardeen and Brattain's ideas.

Scratching page after page into his notebook, one of Shockley's ideas was to build a semiconductor "sandwich." Three layers of semiconductors all piled together, he thought, just might work like a vacuum tube-with the middle layer turning current on and off at will. After some 30 pages of notes, the concept hadn't quite come together so Shockley set it aside to do other work.

The Idea Comes Together

Shockley's January was pretty dismal. He thought he should get sole credit for inventing the transistor-the initial research ideas, after all, had been his own. The Bell Labs attorneys didn't agree. They refused to even put him on the patent. The only thing to do, Shockley decided, was to build a better mousetrap.

As the rest of the group worked merrily away on improving Brattain and Bardeen's point-junction transistor. Shockley concentrated on his own ideas -- never letting anyone else in the lab know what he was up to.

On January 23, unable to sleep, Shockley was sitting at the kitchen table bright and early in the morning. He suddenly had a revelation. Building on the "sandwich" device he'd come up with on New Year's Eve, he thought he had an idea for an improved transistor. This would be three-layered sandwich. The outermost pieces would be semiconductors with too many electrons, while the bit in the middle would have too few electrons. The middle layer would act like a faucet--as the voltage on that part was adjusted up and down, it could turn current in the sandwich on and off at will.

Shockley told no one about his idea. The physics behind this amplifier was very different from Bardeen's and Brattain's, since it involved current flowing directly through the chunks of semiconductors, not along the surface. No one was sure if current even could flow right through a semiconductor and possibly Shockley wanted to test it before discussing it. Or possibly he felt that Bardeen and Brattain had "taken" ideas of his for the point-contact transistor and he didn't want to risk that happening again.

The Eureka Moment

Then, on February 18, Shockley learned it could work. Two members of the group, Joseph Becker and John Shive, were working on a separate experiment. Their results could only be explained if the electrons did in fact travel right through the bulk of a semiconductor. When they presented their findings to the group, Shockley knew he had the proof he needed. He jumped up and for the first time shared his concept of a sandwich transistor to the rest of his team.

Bardeen and Brattain were stunned that they hadn't been filled in before now. It was clear that Shockley had been keeping this secret for weeks. It added still more space to the ever-widening gap that was growing between them.

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