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Registered Member #3637
Joined: Fri Jan 21 2011, 11:07PM
Location: Buffalo, NY
Posts: 1068
I know that Silicon transistors (and now a newer candidate, Silicon Carbide) have more... capability in the power department, but is there really anything that still uses germanium transistors/diodes asides from crystal radio sets? Germanium stuff tends to have a lower voltage drop... so it makes more sense to use them over silicon...
Also, a random though; What would a MOSFET would be like using Germanium dioxide instead of silicon dioxide, or what an IGBT would be like using germanium instead of silicon...
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Germanium transistors were awful by modern standards. They were slow, leaky, and had a limited operating temperature: 80c as opposed to 150 for silicon. They also had to have sealed metal packages because germanium oxide is water soluble, so they can't be passivated and moulded into a lump of plastic like silicon chips normally are.
Also it's been a long time since semiconductor physics, but I think there's something about the crystal structure of germanium that means it's impossible to make a FET.
Germanium power transistors had a niche in low voltage, high current motor controllers for golf carts and the like, but when vertical MOSFETs came along their lunch was well and truly eaten.
The main use for them now is Fuzz Face guitar pedals.
Registered Member #72
Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659
Of course the cool way to use germanium now is to alloy it with silicon, to make silicon-germanium, or SiGe transistors. Several factors faster than straight silicon, and can can be processed in regular silicon foundries, just the way that GaAs or any of the other exotics can't.
Registered Member #1792
Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527
jnbrex wrote ...
I know that Georgia Tech has a germanium processor that operates at 500 GHz.
The press releases sure talked it up, but based on the actual research paper I think they only tested single transistors, and they only got to 500GHz f_t (small-signal unity current gain frequency, not directly related to digital performance) with cryogenic cooling. But that's a long way from making a processor at that frequency, Intel 32nm has a peak f_t above 400GHz but you don't see intel making 400GHz chips
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Germanium vs Silicon
