Research Update: GaN FET produces 174W at 6 GHz

For satellite and cellular base stations, a GaN (gallium-nitride) power FET from Toshiba Corp surpasses the output of GaAs (gallium-arsenide) devices, improving power density by a factor of eight. Currently available GaAs devices are rated at about 90W/6 GHz and 30W/14 GHz, but GaN has higher saturation electron velocity, dielectric breakdown voltage, and operating-temperature range than GaAs. These factors are important for achieving higher power gigahertz-range operation.

The device uses an epitaxial-layer structure, with optimized FET layout and dimensioning, plus a new surface-treatment process for low contact resistance and low gate-leakage current. Toshiba's production also requires a modified version of the conventional stepper process, which is better for mass-production than the electron-beam lithography process that C-band GaN devices commonly use. A GaN power-FET chip measures 2.92×0.71 mm, and the outer cavity of a packaged device with four chips, such as the one in the photo, measures 24.5×17.4 mm. For more, go to www.toshiba.co.jp/about/press/2005_09/pr1201.htm.

Toshiba Corp, www.toshiba.co.jp.