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.
I remember when the 4004 was new.
(Pass some of that dirt)...
Sad but true. Those libraries are being redesigned and the processes are being revisited.
What's even worse? I built the first processor with onboard RAM and ROM...
I can remember making single germanium transistors by placing two indium dots on either side of a wafer, one for the emitter, and a slightly bigger one for the collector, then cooking it with the right temperature/time profile. Take that!
I used paper tape to program an HP DTS70 ... take that
You win. But I still have the alloy junction design handbook...
...as a total aside, what's with the "mark of the Beast" in your tagline...?
I did do some designs with vacuum tubes but I was working with RADAR systems ... BUT I think ya got me ... :<)
And I (a) used paper tape for programming PDP8s and PDP11s and ....wait for it....(b) programmed a TUBE COMPUTER (Stantec Zebra)in the early 60's (2K total core memory).
I don't feel that old.....
I used to work on a uVax ... remember DCL ?
Remember "adventure" ... wumpas
LOL! you've got me beat!
When I "waded into" the SC world, folks were still emoting over all the wonders that "Expanded Contacts" could bring to pass...
I remember the microVAX but I don't recognize 'DCL'.
Dec Command Lanquage
To this day I still use some of the the old VAX file naming protocols. If I write a script I always name it .com even in UNIX
To this day I still use some of the the old VAX file naming protocols. If I write a script I always name it .com even in UNIX
Right on.
I wrote a 'dir' for my unix system, just like DCL had.
Oh, it was just a response to a comment on another thread about chipping kids as a kidnap countermeasure.
It occured to me that when "they" were ready to start chipping us all the'd need to sell the idea.
So I imagined an advertising campaign, star athletes, golf, tennis, baseball, etc. saying "It's all in the wrist".
You know, seeing a 7-10 split being knocked down, the smug bowler eyes the camera and says "It's all in the wrist™!" Then the voiceover says "If Joe Bowldownski is injured, the doctors can treat him faster because his medical records are always with him". Cut to Joe with a couple hot babes buying drinks with a wave of the hand. A sly wink, and "It's all in the wrist™!"...
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