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"So I toyed around in my mind: How can I do this experiment -- I was still being lazy; of course I could have evacuated the thing, but that was the sample that had been fixed up to put down in this thermos and it wasn't exactly conducive to evacuation; and it would have taken some time to do this."-- Walter Brattain, January 1964 (p.28)
"I think I suggested, 'Why, John, we'll wax the point.' One of the problems was how do we do this, so we'd just coat the point with paraffin all over, and then we'd push it down on the crystal. The metal will penetrate the paraffin and make contact with the semi-conductor, but still we'd have it perfectly insulated from the liquid, and we'll put a drop of tap water around it. That day, we in principle, created an amplifier." -- Walter Brattain, January 1964
"This circuit was actually spoken over and by switching the device in and out a distinct gain in speech level could be heard and see on on the scope presentation with no noticeable [sic] change in quality." -- Walter Brattain, December 24, lab notebook
The
Miracle Month
The
Invention of the First Transistor,
November 17-December 23, 1947
Getting Wet
On November 17, 1947, Walter Brattain dumped his whole experiment into a thermos of water. The silicon contraption he'd built was supposed to help him study how electrons acted on the surface of a semiconductor -- and why whatever they were doing made it impossible to build an amplifier. But condensation kept forming on the silicon and messing up the experiment. To get rid of that condensation, Brattain probably should have put the silicon in a vacuum, but he decided that would take too long. Instead he just dumped the whole experiment under water -- it certainly got rid of the condensation!
Out of the blue, the wet device created the largest amplification he'd seen so far. He and another scientist, Robert Gibney, stared at the experiment, stunned. They began fiddling with different knobs and buttons: by turning on a positive voltage they increased the effect even more; turning it to negative could get rid of it completely. It seemed that whatever those electrons had been doing on the surface to block amplification had somehow been canceled out by the water -- the greatest obstacle to building an amplifier had been overcome.
Putting the Idea to Use
When John Bardeen was told what had happened he thought of a new way to make an amplifier. On November 21, Bardeen suggested pushing a metal point into the silicon surrounded by distilled water. The water would eliminate that exasperating electron problem just under the point as it had in the thermos. The tough part was that the contact point couldn't touch the water, it must only touch the silicon. But as always, Brattain was a genius in the lab. He could build anything. And when this amplifier was built, it worked. Of course, there was only a tiny bit of amplification -- but it worked.
Big Amplification
Once they'd gotten slight amplification with that tiny drop of water, Bardeen and Brattain figured they were on the road to something worthwhile. Using different materials and different setups and different electrolytes in place of the water, the two men tried to get an even bigger increase in current. Then on December 8, Bardeen suggested they replace the silicon with germanium. They got a current jump, all right -- an amplification of some 330 times -- but in the exact opposite direction they'd expected. Instead of moving the electrons along, the electrolyte was getting the holes moving. But amplification is amplification -- it was a start.
Brattain Makes a Mistake
Unfortunately this giant jump in amplification only worked for certain types of current -- ones with very low frequencies. That wouldn't work for a phone line, which has to handle all the complex frequencies of a person's voice. So the next step was to get it to work at all kinds of frequencies.
Bardeen and Brattain thought it might be the liquid which was the problem. So they replaced it with germanium dioxide -- which is essentially a little bit of germanium rust. Gibney prepared a special slab of germanium with a shimmering green oxide layer on one side. On December 12, Brattain began to insert the point contacts.
Nothing happened.
In fact the device worked as if there was no oxide layer at all. And as Brattain poked the gold contact in again and again, he realized that's because there wasn't an oxide layer. He had washed it off by accident. Brattain was furious with himself, but decided to fiddle with the point contact anyway. To his surprise, he actually got some voltage amplification -- and more importantly he could get it at all frequencies! The gold contact was putting holes into the germanium and these holes canceled out the effect of the electrons at the surface, the same way the water had. But this was much better than the version that used water, because now, the device was increasing the current at all frequencies.
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Bringing it All Together
In the past month, Bardeen and Brattain had managed to get a large amplification at some frequencies and they'd gotten a small amplification for all frequencies -- now they just had to combine the two. They knew that the key components were a slab of germanium and two gold point contacts just fractions of a millimeter apart. Walter Brattain put a ribbon of gold foil around a plastic triangle, and sliced it through at one of the points. By putting the point of the triangle gently down on the germanium, they saw a fantastic effect -- signal came in through one gold contact and increased as as it raced out the other. The first point-contact transistor had been made.
Telling the Brass
For a week, the scientists kept their success a secret. Shockley asked Bardeen and Brattain to show off their little plastic triangle at a group meeting to the lab and the higher-ups on December 23. After the rest of the lab had a chance to look it over and conduct a few tests, it was official -- this tiny bit of germanium, plastic and gold was the first working solid state amplifier.
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