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Why don't they make germanium power diodes for their lower voltage drop? I have used a diode connected junk-box germanium power transistor for a oneoff low voltage in house current measuring job because it out performed a Phillips BYV1040 1Amp 40V silicon schottky. Could they make a germanium schottky diode? Would its voltage drop be about half of a Si schottky? Could such a proposed device be useful in energy harvesting despite probably having a low PIV and high reverse leakage current ?

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A couple reasons Silicon is much more plentiful then germanium, so much less expensive.
Silicon is much easier to process. Silicon has a much higher peak inverse voltage rating (breakdown).
Silicon is much more tolerant of high temperatures then Germanium... Especially important in a power diode. A germanium diode is easily destroyed by moderately high temperatures, typically less then half of what silicon can handle. Silicon junctions have a much lower leakage than germanium.

As compared to schottky diodes, germanium diodes have a much softer knee as they begin to conduct. The shottky diode switches pretty much instantly from blocking to conduction, but the germanium one will follow a curve.
Silicon schottky's also have lower leakage and greater current capacities (as above) then germanium, and share the same plentiful element base and ease of manufacturing.

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    \$\begingroup\$ to add one more negative. Germanium diodes will self dope and degrade from cosmic rays present across the surface of the earth . The germanium transmutes to gallium (n-type dopant) from occasional high energy gamma particles impinging on isotopic impurities in the crystal as well as Arsenic (p-type) from alpha particles caused by particle showers. \$\endgroup\$ – crasic Sep 1 '15 at 17:17
  • \$\begingroup\$ The softer knee mentioned by R Drast is probably why some Audiopliles and some musicians prefer the sound of germanium to silicone.Guitarists that make and use fuzz boxes tend to prefer the germanium diode for better sounding distortion . \$\endgroup\$ – Autistic Sep 8 '15 at 4:23
  • \$\begingroup\$ CRASIC said something interesting.does this mean that germanium semiconductors or any other low band gap stuff has a shelf life which is dependant on background radiation? \$\endgroup\$ – Autistic Sep 17 '15 at 20:53
  • \$\begingroup\$ Yeah, germanium diodes and transistors are used in guitar effects. This doesn't mean they are more "hi-fi", rather they create more pleasing guitar distortion when overdriven. \$\endgroup\$ – peufeu Jan 2 at 21:51

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