Chips made of the SiGe alloy have increased performance and reduced power consumption over chips made of pure Si. Potential applications of ultra-high-frequency SiGe circuits with extreme levels of transistor performance include cell phones and many more advanced communications systems, defense systems, space electronics platforms, and remote sensing systems. Ultra-high-frequency SiGe technology is desirable because of the low cost of standard high-volume silicon-based manufacturing processes.
500 GHz Transistor
In June 2006, the first silicon-germanium (SiGe) transistor able to operate at frequencies above 500 GHz was demonstrated by a research team from IBM and the Georgia Institute of Technology (Georgia Tech). This high speed world record was achieved at a an extremely cold 4.5 degrees Kelvin (-451 degrees Fahrenheit) attained by liquid helium cooling. photograph shows a SiGe chip inside a cryogenic test station observed by a Georgia Tech researcher. At approximately 350 GHz, the performance of the transistor at room temperature was also impressive. Much higher (near-terahertz [THz]) operational frequencies at room temperature are believed to be attainable with future SiGe technology.
More information on 500 GHz transistor from the Georgia Tech webpage.