Messenger - Vol. 2, No. 1, Page 13 Fall 1992 On the trail of faster, smarter electronics Pocket calculators, medical laser devices, automobile ignitions and the tiny, LED Watchman televisions all rely on semiconductors. Semiconductors are materials, like silicon, that can conduct electricity, though not as well as metals do. They are needed to make electronic devices such as transistors, integrated circuits and microchips that are the basis of today's micro-electronic industry. "There is an ongoing quest for higher performance from semiconductors," says James Kolodzey, associate professor of electrical engineering. "There are groups looking for new structures, different shapes and sizes, and others looking for better materials. Right now, I am leaning toward new materials." Kolodzey is working at a molecular level to restructure a silicon-germanium semiconductor that will be useful for smaller, faster and smarter electronic devices. "Silicon semiconductors are the most common and pervasive, but silicon cannot easily emit light," he says. "A gallium-arsenide semiconductor can emit light, but it is difficult to process, so the search goes on." Modern techniques for growing crystals, such as molecular beam epitaxy, or MBE, make it possible to form new structures and layers in a semiconductor. "Silicon germanium can be made as an alloy and as layered structures in which one region has more germanium than another," Kolodzey says. "These are called hetero-structures, and the MBE process makes it possible to create light emitters from materials not previously thought capable of this." A silicon-germanium semiconductor would be compatible with the commonly used silicon, so this combination is promising, he says. However, sometimes, the electrical/optical properties malfunction because the larger germanium atom cannot line up with the silicon substrate. "We are trying to compensate for the strain by adding the diamond form of carbon," Kolodzey says. While on leave in Germany, Kolodzey successfully grew a sample of the silicon-germanium-carbon alloy using a chemical vapor deposition process, and its electronic properties were evaluated at Delaware in collaboration with Mark Barteau and Doug Buttrey in the Department of Chemical Engineering. The early measurements were encouraging, Kolodzey says, and were reported at the spring Material Research Society meeting. He expects to have some results from the MBE process by this fall. "Few groups in the world have made this material before, and the early measurements of properties are encouraging," Kolodzey says. "The idea may turn out to be a bust, but this type of basic research is always important. It teaches students how to analyze materials and make new devices, and future researchers learn what does and what does not work out. "On the other hand, if our idea works, this new semiconductor could result in faster circuitry and improve the performance of high-speed computers, medical imaging systems and even telephone communications," Kolodzey says. --Cornelia Weil