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 ?
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.