Chuck Harris
Brooke Clark on his PRC68.com website reminisced about his
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days working for Aertech testing tunnel diodes. This excerpt is gratuitously stolen from his website: "Early tunnel diodes were made by hand one at a time. A small sphere of metal was alloyed to a chip of semiconductor material (Germanium, Gallium arsenide, or Gallium Antimonide) The chip was die attached into a metal ceramic package and then had a gold screen bonded from one side of the package flange to the metal sphere and to the other side of the package, like a bridge. Then the diode was etched in a caustic solution forming a mushroom shaped cross section. The stem of the mushroom was extremely narrow and the actual junction was in this stem. An improvement to that process involved gluing a couple of very small diameter glass rods (made by pulling a hot glass rod) on either side of the metal ball after sintering and before attaching the mesh. The rods tended to take some of the stress off of the tunnel junction and make the diode much more reliable. The coefficient of thermal expansion of the glass was chosen to be close to the material of the tunnel diode. Later a "planar process" was developed that allowed back diodes to be made at the wafer level. This is used at Metelics. " I recall that at University of Maryland one of my professors, HC Lin, had his graduate students making diodes and LED's by hand in his lab... Nothing but bench work... Perhaps with a little guidance from Brooke, some members could start making tunnel diodes? -Chuck Harris Tom Lee wrote: Great, Jeff. It looks like we¡¯ve managed to narrow the window considerably. So it¡¯s looking like the Age of the TD started around 1961 and ended almost exactly 20 years later. Not a bad run for an oddball device. |