In keeping with Ibuka's ideal of "having youngsters come in contact with science as early as possible," Sony today still takes an active part in science-related exhibitions aimed at children. These activities have gained Sony much public acclaim. One such event was the "Children's Electronics Exhibit" held at the main branch of the Mitsukoshi Department Store in Nihombashi, Tokyo.
Mitsukoshi's PR manager Shigeru Okada offered Sony free use of the main store's large exhibit and roof areas for one week. Okada suggested that Sony display some of its unique technology that would be of interest to children, as the exhibition period coincided with the holiday week which included Children's Day.
After much consideration, it was decided to display a transistor and a transistor radio production line complete with fifteen female workers who peered into microscopes and assembled parts. These assembly lines, along with a solar-powered helicopter and airplane, Japan's first VTR, and a fully automated driverless car, were big hits among children and adults as well.
The exhibit was a great success, easily topping 200,000 visitors over the week-long period, making it the largest drawing card in Mitsukoshi's history. In fact, the crowds were so large that ropes had to be drawn along all the staircases to control the long waiting lines. The temperature in the hall was 3c higher than the rest of the building.
By that time, many Japanese companies had begun to produce transistors. Their manufacturing processes were carefully guarded secrets, however, and the very idea of putting them on public display was unthinkable. Only Sony had the courage and resolve to expose its technology to public view.
Then in June, Sony announced the successful testing of the Esaki Diode, also known as the tunnel diode, which Sony researcher Leona Esaki invented.
Two years earlier, Iwama, then manager of the Semiconductor Department, had been trying to improve the poor yield percentage of the new 2T7 grown junction transistor. Tetsuo Tsukamoto of the Semiconductor Department had developed it to replace the earlier 2T5 model.
During the six months he was bedridden while recovering from the side effects of penicillin, Tsukamoto had constantly considered replacements for the 2T5, which had a poor production yield and performance. High frequency transistors require the creation of a thin base layer with a large amount of impurities. An emitter layer, also with many impurities, has to be deposited on top of that. The higher the effective impurity concentration in the emitter, the greater the transistor's amplification. The problem was determining the upper limit of impurity concentration. Tsukamoto hit upon the idea of using phosphorous instead of the conventional antimony as the impurity in the emitter. Immediately after his recovery, Tsukamoto conducted experiments to corroborate his theory. The results were unprecedented, and frequency characteristics five times higher than those of the 2T5 model were obtained. Beyond certain levels, antimony impedes the formation of germanium monocrystals and thus cannot be used in large amounts. Phosphorous, on the other hand, can be mixed with germanium in unlimited volumes, and the higher the concentration, the better the crystals. And because phosphorous does not diffuse as much as antimony in germanium, the thickness of the base can easily be made to design specifications.
Iwama was overjoyed with the new transistor, called the 2T7. As noted in the guinea pig article((See Part I, Chapter 8
), the transistor field was no longer Sony's unchallenged domain. In fact, the transistor makers were already involved in a fierce price war. Sony felt that since its products were more expensive, it would have to win out with new products and was forced to expand into shortwave and FM radio. Thanks to the 2T7, however, it appeared as though the problem of developing a high frequency transistor for use in these new products had been resolved in a single stroke.