ONR-sponsored scientists at Cornell University are developing a new generation of transistors based on gallium nitride. The new transistors operate at microwave frequencies and promise to deliver up to 100 times as much power as the semiconductors now used in cellular telephones, military radar and satellite transmitters. The added power will give these devices a greater range of communication and more energy efficiency. The researchers have tested gallium nitride transistors with output power of up to 2.2 watts per millimeter at a frequency of 4 gigahertz and expect to see power figures five time higher once they improve thermal management. Among the important uses for gallium nitride transistors will be a new generation of communications satellites serving cellular telephone users. New systems will use hundreds of low-orbit satellites that allow users to make phone calls anywhere on Earth.