Posted on 04/27/2023 12:30:22 PM PDT by Red Badger
The germanium-tin processor was fabricated at the Helmholtz Nano Facility, the Helmholtz Association's central technology platform for the manufacturing of nanostructures and circuits. Credit: Forschungszentrum Juelich
Scientists at Forschungszentrum Jülich have fabricated a new type of transistor from a germanium–tin alloy that has several advantages over conventional switching elements. Charge carriers can move faster in the material than in silicon or germanium, which enables lower voltages in operation. The transistor thus appears to be a promising candidate for future low-power, high-performance chips, and possibly also for the development of future of quantum computers.
Over the past 70 years, the number of transistors on a chip has doubled approximately every two years—according to Moore's Law, which is still valid today. The circuits have become correspondingly smaller, but an end to this development appears to be in sight.
"We have now reached a stage where structures are only 2 to 3 nanometers in size. This is approximately equal to the diameter of 10 atoms, which takes us to the limits of what is feasible. It doesn't get much smaller than this," says Qing-Tai Zhao of the Peter Grünberg Institute (PGI-9) at Forschungszentrum Jülich.
For some time now, researchers have been looking for a substitute for silicon, the primary material used in the semiconductor industry. "The idea is to find a material that has more favorable electronic properties and can be used to achieve the same performance with larger structures," the professor explains.
The research is in part focused on germanium, which was already being used in the early days of the computer era. Electrons can move much faster in germanium than in silicon, at least in theory. However, Qing-Tai Zhao and his colleagues have now gone one step further. To optimize the electronic properties even further, they incorporated tin atoms into the germanium crystal lattice. The method was developed several years ago at the Peter Grünberg Institute (PGI-9) of Forschungszentrum Jülich.
"The germanium–tin system we have been testing makes it possible to overcome the physical limitations of silicon technology," says Qing-Tai Zhao. In experiments, the germanium–tin transistor exhibits an electron mobility that is 2.5 times higher than a comparable transistor made of pure germanium.
Another advantage of the new material alloy is that it is compatible with the existing CMOS process for chip fabrication. Germanium and tin come from the same main group in the periodic table as silicon. The germanium-tin transistors could therefore be integrated directly into conventional silicon chips with existing production lines.
High potential for the computers of the future Apart from classical digital computers, quantum computers could also benefit from the germanium–tin transistor. For some time, there have been efforts to integrate parts of the control electronics directly on the quantum chip, which is operated inside a quantum computer at temperatures close to absolute zero. Measurements suggest that a transistor made of germanium-tin will perform significantly better under these conditions than those made of silicon.
"The challenge is to find a semiconductor whose switching can still be very fast with low voltages at very low temperatures," explains Qing-Tai Zhao. For silicon, this switching curve flattens out below 50 Kelvin. Then, the transistors need a high voltage and thus a high power, which ultimately leads to failures of the sensitive quantum bits because of the heating. "Germanium–tin performs better at these temperatures in measurements down to 12 Kelvin, and there are hopes to use the material at even lower temperatures," says Qing-Tai Zhao.
In addition, the germanium–tin transistor is a further step towards optical on-chip data transmission. The transmission of information with light signals is already standard in many data networks because it is considerably faster and more energy-efficient than data transfer via electrical conductors. In the field of micro- and nanoelectronics, however, data is usually still sent electrically.
Colleagues from the Jülich working group of Dr. Dan Buca have already developed a germanium-tin laser in the past that opens up the possibility to transmit data optically directly on a silicon chip. The germanium-tin transistor, along these lasers, provides a promising solution for the monolithic integration of nanoelectronics and photonics on a single chip.
The paper is published in the journal Communications Engineering.
More information: Mingshan Liu et al, Vertical GeSn nanowire MOSFETs for CMOS beyond silicon, Communications Engineering (2023).
DOI: 10.1038/s44172-023-00059-2
Tech Ping!....................
I believe the next generation of circuits will be optical in there basic nature. We already have optical switches but the current design is far larger than current electrical chips.
One good thing about germanium is it’s lower forward bias voltage drop is less than silicon’s by about half.
Germanium vs Silicon transistors in fuzz-tone pedals has been a long-running debate among guitar players:
“Quick Summary: Germanium fuzz is less harsh, more expensive and gives a vintage sound. Silicon fuzz is harsher with more gain. Silicon fuzz pedals are usually cheaper and easy to mass produce in today’s market because most use modern low cost transistors.
So, this MAY be good news for guitar players! :-D
The coal deposits near Xilinhaote, Inner Mongolia, contain an estimated 1600 tonnes of germanium.
IOW, Red China has the largest deposits.
The difference is probably the Germanium’s lower forward bias voltage drop. Or that it probably creates less harmonic distortion than silicon...........................
Geranium Valley
(Yeah, I know the spelling is different)
But I think that’s how it would go...
Ironically for years the only place you could find germanium was in small signal diodes like the ubiquitous 1N25, and in very high power transmission line rectifiers used by the power companies (where the lower Vbe was significant).
yup
And how much does an eight inch platter of germanium cost?
this would have been nice forty years ago
today
not so much
That small voltage drop is very useful when making crystal radios, or any small signal front end.
The original 60's fuzz pedals (notably the Gibson Fuzz-Tone and the Arbiter Fuzz-Face) used Germanium transistors, and modern builds of those classic circuits still do. Silicon simply does not behave or sound right in those simple circuits. I have a Fuzz-Face that is the best distort pedal I've owned in 60 years of guitar playing. Three Ge transistors, maybe a half-dozen passive components. Simple and beautiful.
More complex circuits benefit from silicon because they typically work with boosted signals, or they're using IC op-amps instead of discrete transistors. But you pay a price in increased noise and diminished clarity.
There's one big problem with Ge-based pedals, though. They misbehave when they get hot, whether in the studio or onstage. The transistors' bias changes as the leakage currents drift, and the pedal gets choppy and can stop working altogether (e.g. read the history of Hendrix and the Fuzz-Face). I learned when playing outdoors to shield my pedal from direct sunlight. But if you manage the temperature, Ge pedals are the best.
Ge transistors will never disappear as long as guitarists are around!
Guitar players love distortion, it just has to be the right kind of distortion.
True, that is how ‘fuzz’ started in the first place, with an amp that had a bad tube......................
You are absolutely right about temperature problems with GE transistors. I had an old portable record player I used to take to record shows to sample the wares. If it sat too long in a hot car, the output dropped to near zero.
A while back, I repaired a vintage germanium-based Japanese fuzz box which had a bad power switch and some wiring problems.
I could never figure out how the thing worked, but what it did was introduce a spike into the waveform (it was not a simple clipper). When fed with a sine wave, the spike only appeared on the downward slope, about 1/3 down from the peak. The eventual buyer described the sound as “fabulous”.
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