Sept. 29, 1999
Contact: Chris Curran
ENGINEERING FACULTY "LIGHT UP" UC,
TECHNIQUE HAS WIDE-RANGING ELECTRONICS APPLICATIONS
Cincinnati -- Novel semiconductors produced in the University of Cincinnati College of Engineering are highlighted on the cover of this month's Materials Research Society Bulletin.
The opto-electronic device literally lights up the university's "double horseshoe" logo using gallium nitride doped with the rare earth elements such as erbium, europium and thulium. Together, the wide range of colors nearly duplicates or exceeds the spectrum produced by tube technology and television.
"If you want to have full color, three-color displays based on semiconductor technology instead of tubes ... If you want flat panel displays, this will take up less space and use much less power," said Andrew Steckl, Ohio Eminent Scholar and Gieringer Professor in electrical and computer engineering at UC.
Steckl's Nanoelectronics Laboratory recently received a $1 million grant from the National Security Agency to develop photonic devices which can store and process more information more quickly. A previous grant focused on the telecommunications aspects of photonics.
Both projects require the use of multiple techniques for producing the next generation of semiconductors. Steckl said batch processing is fine for mass producing simple chips, but developing the technology for the new semiconductors required MBE (molecular beam epitaxy) and integrating the circuitry required a FIB (focused ion beam) technology.
"Ions have energy, mass, and charge, so they're the most versatile," said Steckl, explaining why ion beams are preferred over virtually massless electrons and photons which are typically used to make semiconductor devices. "You can use both their energy and their momentum, and you can manipulate them."
In addition, you can customize your chips by changing conditions during processing, which cannot be done with conventional technology. That takes more time, an acknowledged disadvantage of beam technology, but Steckl says the flexibility is demonstrating that FIB and other beam technologies have a future as bright as his opto-electronic devices.
"If I just wanted to make large numbers of the same transistor or laser or waveguide, then I wouldn't need it," admits Steckl. "But I want to make a working circuit. Here, I design a laser, here a waveguide...to that I may add an amplifier or a divider or a combiner or a detector, and so on. Each of these components is going to have different requirements, so that is the problem. We're trying to address how to integrate them. FIB and MBE are two of the keys to solve this problem."
Most important, photonics allows better integration between chips and from board to board. Traditional microelectronics is limited by the number of connections to avoid wires short-circuiting each other.
"Wires cannot cross, so electrical signals sent by wire have this limitation in terms of their density," explained Steckl. "Optical signals can cross, so you can go with much, much higher density. Photonic components are the ideal components for these interconnects."
The ultimate research goal is to develop a storage system which can handle one terabyte of storage with processing times in micro- to nanoseconds. Although Steckl isn't certain of the ultimate applications by the National Security Agency, he does foresee many other applications for his devices.
"Commercial uses?," asks Steckl. "My guess is 'Yes.' The government tends to develop the most challenging applications, because their needs are the most difficult. Some form of that technology generally hits the commerical marketplace and really pushes the technology. That's why it's important to have federal R&D support."
The full-color possibilities of the rare earth-doped semiconductors are also likely to have applications in the medical field. "In biology and medicine, you sometimes need a specific light color or multiple colors to get a clear diagnosis, or trigger a biochemical reaction, or evaluate a biological system and get an unambiguous picture," said Steckl.
Other materials produced in Steckl's UC laboratory emit light in the infrared, a key wavelength for telecommunications. "We have yellow and orange too. We're constantly working on this and having great fun coming up with devices which emit light in various combinations of colors."
Steckl's collaborators in the Nanoelectronics Laboratory are post-doctoral fellows Ron Birkhahn, David Chao, and John Chen; and graduate students Jay Cheng, Robert Chi, Irving Chyr, Mike Garter, Bob Hudgins, Jason Heikenfeld, Boon Lee, and Don Lee.