Recreating the First Transistor

Kevin Aylesworth is a Senior Program Officer at the National Research Council. Although his job these days revolves around science policy rather than building things in the lab, Aylesworth—an experimental physicist by training—happily accepted our challenge to build a working replica of the first transistor. (He says he thought it was a "cool thing to do.") But just because it had been done before doesn't mean it was easy.

First he had to find out how it had been built. He read through as much information from the time period as he could, including Walter Brattain's lab notes. Brattain's lab notes are meticulous—filled with detailed descriptions of the results of testing all his devices—but one thing he didn't write down was exactly how to build the thing. There was, however, a drawing of the transistor point, labeled with its dimensions. By comparing this to photos of the transistor, Aylesworth determined the size of every other part of the device.

Walter Brattain's meticulous lab notes.

The next step was to get the right materials. This information was all well documented, right down to the kind of glue (Duco Cement) that was used. The tough part was in finding the right kind of germanium crystal. "I wasn't able to get the same germanium," says Aylesworth. "It just doesn't exist anymore." Brattain used tin-doped germanium in his device, but from what we now know of semiconductors it doesn't make sense that tin could have created the transistor effect. The scientists Aylesworth talked to suggested there were probably additional impurities in the tin to make that first transistor work. So instead of the tin-doped germanium, Aylesworth used a worthwhile substitute: some old germanium slices from Nick Holonyak.

Aylesworth then got Johnson Mathey Co. to donate some gold foil (normally they only sell their products to research labs, but were happy to give the tiny bit of foil over for what they thought was an interesting project), and found some tiny wires in the garage of a friend who is an amateur radio hobbyist. Now he just had to put the contraption together.

The germanium had to be etched, or made smooth so that no impurities would interfere with the transistor effect. Aylesworth claims to be a "klutz by nature," and had hoped he wouldn't have to use chemicals for the etching. No such luck. He tried to etch the crystals with a machine and couldn't get it to work. So he turned to hydrofluoric acid. On first dropping his germanium into the beaker, the acid began to boil furiously, spewing off ominous orange fumes. The concentration of acid was far stronger than the label had said, and Aylesworth barely rescued that piece of germanium. But after diluting the acid, all went smoothly. Sort of.

Aylesworth's masterpiece.

"They had pretty explicit instructions on how things were constructed, so the rest of it was fairly straight-forward," says Aylesworth. "Testing it was another problem." He collected some old power supplies and oscilloscopes to provide an input signal and to measure the output. But the signal on the oscilloscope screen was too noisy to allow Aylesworth to rapidly find "good" spots on the germanium. He spent hours fiddling with things without any luck.

In the end, however, the easiest thing was to do just what Bardeen and Brattain did: hook the transistor up to a set of headphones and listen. Aylesworth thinks his transistor was a little more finicky than the original—perhaps it wasn't as clean—and it took a lot of trial and error to find a spot that would get the device to work. But after about an hour and a half of moving the contacts around on the germanium, searching for a sweet spot, he could easily hear the transistor amplifying the input signal, a kind of loud buzzing.

Ecstatic, Aylesworth called Transistorized! executive producer Eliene Augenbraun at around midnight, and paraphrasing the immortal words of Walter Brattain (and without preamble) screamed, "We've got gain!

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Kevin Aylesworth on his late-night success:
"I got very excited. I called Eliene Augenbraun and told her, 'We've got gain!' She was very happy; I was very happy. I was a little hesitant to tell her that the gain was probably not much more than one, if even that, but we were all very happy."

SPECIAL THANKS:
To the Naval Research Laboratory, which donated space and equipment for this project, and to the American Physical Society (where Kevin was working at the time), for donating Kevin's precious time to make the thing!

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