Posted on 04/15/2005 2:06:56 PM PDT by LaserLock
A pair of physicists in the US has built the fastest ever transistor: one that can operate at a frequency of over 600 gigahertz. Developed by Walid Hafez and Milton Feng at the University of Illinois at Urbana-Champaign, the device is made from the semiconductors indium phosphide and indium gallium arsenide (Appl. Phys. Lett. 86 152101). The work demonstrates the feasibility of making transistors that can operate at frequencies of several terahertz, which could be used in ultrafast communications, high-speed computing, medical imaging and sensors.
The new device is a so-called bipolar transistor, which is very different from the more well-known field-effect transistor. In it, electrons are injected from the "emitter" terminal, travel towards the "base" and are then received by the "collector", an arrangement that allows the device to work faster than a field-effect transistor.
Hafez and Feng have previously built a high-frequency bipolar transistor, but this earlier work focused on reducing the time it takes electrons to pass through the device by minimizing the device's vertical thickness. Their new research further increases electron speeds through the device by slightly varying, or "grading", the composition of the semiconductor layers. This, say the researchers, lowers the band gap in selected areas of the transistor and makes it easier for electrons to travel across the device.
The two physicists have shown their transistor can operate at a frequency of 604 gigahertz, a new record. However, according to Hafez, what is more important is that they have developed a technology that could be used to build transistors operating in the terahertz range. "Projections from our earlier high-frequency devices indicated that in order to create a transistor with a cutoff frequency of 1 terahertz, the devices would have to operate above 10,000 degrees C," he says. "By introducing the grading into the layer structure of the device, we have been able to lower the potential operating temperature for a terahertz transistor to within an acceptable range."
Devices operating at terahertz frequencies (the far infrared) could be used in communications applications or as sensors to detect toxic gases. They could also be used for medical imaging, since the radiation is long enough to penetrate skin and image what lies underneath.
The researchers' next step is to show that their devices can be assembled into circuits.
Did I get your extra points?
Old habits are hard to break aren't they .....
Clever -- and well done!
Thank yew.
The Anna Kournikova ad was better, but I didn't want to have to post a picture...
Indeed! I still capitalize the first two letters of variable names -- because variable names in AppleSoft Basic consisted of two aplha chars (but you could use additional following letters as mnemonics). And, of course, the first Apple //s were uppercase-only ...on 40-character lines...
7400, something ttl? 555, some kind of op-amp?
Since we are going to go way back, what is an ignatron? I think everyone is gone from here, too bad!
555 is a timer ... it was used a lot in the 70's and 80's
So much for the recently heralded end to Moore's Law...
"555, 556, whatever it takes"
220, 221, whatever it takes..... - Mr. Mom
Indium Phosphide and Indium Gallium Arsenide Linked to Cancer in Children
The first paragraph would read, "Presidential candidate Hillary Clinton related her concern for the children who are exposed to possible cancer causing chips in their Playstations..."
"7400, something ttl? 555, some kind of op-amp?"
perhaps you refer to the 741 Op Amp......
"So much for the recently heralded end to Moore's Law..."
yes, but every 18 months or so they get close to being half right......
Amusing how a thread about future ultrasupermegafast transistors degenerates into a "my transistors were slower than yours" old-timer's argument. :-)
And yes, I knew the 7400, 555, and still have the brown/yellow TI TTL book around here somewhere, plus a couple others, and recognize most of the covers shown in this thread. Recall stringing three 74xx type inverters in a loop just to see how fast it would oscillate (rate will come to me in a few days; pretty fast then, boring slow now).
Strictly speaking, Moore's Law only addressed physical size of transistors. That it works for speed, density, etc. is incidental.
Hardcover.
"In his original paper, Moore observed an exponential growth in the number of transistors per integrated circuit and predicted that this trend would continue."
It seems like he was talking about density to me, which has to correlate pretty closely with performance. Number of transistors per IC = higher performance.
PING
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.