Above : Fujitsu's Newly-Developed GaN HEMT Amplifier Chip

ASIA : Fujitsu Laboratories announced that it has developed a gallium nitride (GaN) high electron mobility transistor (HEMT) amplifier which achieves the world's highest power output of 174 watts at 63 volts, while demonstrating unprecedented record drain efficiency of 40%, fulfilling W-CDMA system requirements for base stations. This breakthrough represents a significant step forward in making smaller and more energy efficient base stations for 3G mobile networks, and overcomes the technical hurdle for output needs exceeding 150 watts required for realistic application in 3G mobile systems.

Details of this technology will be presented at the International Electron Devices Meeting (IEDM) in Washington, D.C. on December 9.

Fujitsu's new technology uses GaN HEMT to produce stable power output at high voltage. Fujitsu has discovered that technical problems such as potential device failure and unstable output, which were observed when voltage exceeded 50 volts, are attributable to non-uniformity and defects in the gallium nitride epitaxial layer. By improving the uniformity of the HEMT epitaxial growth and through growth condition optimization, Fujitsu has succeeded in enabling high-voltage operation.

The optimized epitaxial layer minimizes the phenomena of output and efficiency falling at high voltages. This enables actualization of unprecedented 174-watt output at 63-volt operation (Figure 2). In addition, regarding maximum power-added efficiency (*4), Fujitsu has achieved world-class 54% efficiency for high-output devices.

The most critical factor for moving toward realistic application of this technology is the ability for high-efficiency amplification that conforms to 3G mobile communication base station standards, such as W-CDMA specifications. Fujitsu's GaN HEMT amplifier, when supplied with 60 or more volts of power, satisfies the W-CDMA (*5) specification for adjacent channel leakage (*6), while also achieving the record-setting drain efficiency (*7) of 40%. Proven distortion compensation at 60 volts or higher, achieved by Fujitsu, is the world's first.

As demonstrated by these results, Fujitsu's new GaN HEMT amplifier delivers high performance to transmission amplifiers for 3G mobile communication base stations, contributing significantly to the development of base station systems that are smaller and more cost and energy efficient. Moreover, it clears the practical hurdle of generating power output in excess of 150 watts.