Oki Electric Develops Power GaAs MESFET with World's Highest Drain Efficiency

[photo] KGF1934

Tokyo, Japan, April 19, 2005 -- Oki Electric Industry Co., Ltd. (TSE: 6703) today announced it has developed a power Gallium Arsenide (GaAs) Metal Semiconductor Field Effect Transistor (MESFET)(*1) for 10watt level wireless communication, which achieves the world's highest drain efficiency(*2). Oki plans to start sample shipment of this new product, KGF1934, from April 2005 for transmitter power amplifiers for various wireless base stations such as 3G mobile phones including W-CDMA and CDMA2000. Volume shipment starts June, targeting to sell 10,000 units per month.

"We succeeded in developing a GaAs MESFET that enables high output, high efficiency and high breakdown voltage, which has been difficult in the past. By achieving this breakthrough, we believe the KGF1934 will contribute in enabling smaller wireless base stations for business-use wireless communications and 3G mobile phones," said Masayuki Tsuboi, President of Optical Components Company at Oki Electric. "Because it can reduce 40% of the power consumption, our GaAs MESFET can offer the world's highest drain efficiency to our customers."

To expand communication range and speed for wireless communication systems, underground malls and buildings in urban areas use microcells, covering a small range with multiple base stations. To fit microcells or narrow indoors space, smaller base stations are in demand, requiring power transistors with lower power consumption, higher efficiency and smaller heat dissipation. To improve high frequency characteristic of power GaAs MESFET, it is effective to narrow the gate length or raise the channel(*3) impurity concentration to enhance electron transfer rate. This, however, reduces the breakdown voltage that can destroy the gate, which made it impossible for power GaAs MESFET to operate on high voltage.

To achieve both the high efficiency and high voltage operation, Oki used gate recess structure(*4) and optimized layer structure of the channel region. As a result, Oki established a balance between a high drain breakdown voltage of over 20V and a high drain efficiency of over 55% with a 10W output power at 1db compression point(*5). The drain efficiency of this transistor is as high as 25% at the normal operating output power level of 2W. With these characteristics, the KGF1934 can reduce power consumption by 40% and can realize the best performance as the driver stage amplifier.

Based on the KGF1934, Oki plans to look into developing high frequency power transistors that are highly efficient with high output covering 6GHz range that responds the next generation wireless communication, WiMAX(*6).

[Glossary]

*1 GaAs MESFET: A metal semiconductor field effect transistor using gallium arsenide compound semiconductor that consists of three electric terminals, including the gate, source and drain, and a channel for electron to flow. GaAs is suitable for high frequency amplifier because its mobility is five times higher than that of silicon.
*2 Drain efficiency: The ratio of output RF power divided by the applied DC power. Because amplifiers for 3G mobile phone base stations operate on a maximum output of 1/3 to 1/8, to comply with linearity standards, efficiency in output power is important.
*3 Channel: The electron path formed in layer when impurities are injected into semiconductor. Transistor's high frequency performance can be improved by the carrier density and thickness of the channel due to the increased electron transfer rate.
*4 Recess structure: A transistor gate structure that forms a gate electrode in a etched trench (recess). This structure reduces parasitic resistance between source and gate, and reduces the surface leak current, which leads to the improved high frequency performance and high voltage operation.
*5 1db compression point: A signal level at which a nominally linear RF device's gain is degraded by 1db due to saturation.
*6 WiMAX (Worldwide Interoperability for Microwave Access):: Another name for IEEE802.16 wireless networking specification with a frequency range of 2 to 11GHz, covering 6 to 50km range and a communication speed of maximum 75Mbps.

About Oki Electric Industry Co., Ltd.

Founded in 1881, Oki Electric Industry Co., Ltd. is Japan's first telecommunications manufacturer, with its headquarters in Tokyo, Japan. With the corporate vision, "Oki, Network Solutions for a Global Society," Oki Electric provides top-quality products, technologies and solutions to its customers through its info-telecom system business, semiconductor business and printer business. All three businesses functions as a collective force to create exciting new products and technologies that satisfy a spectrum of customer needs in various markets. Visit Oki's global web site at http://www.oki.com/.

Notes:

Names of companies and products are trademarks or registered trademarks of the respective companies.

Press Contact:

For Europe and Americas: Public Relations Division: Phone: +1-408-737-6479

For Asia and Other Areas: Public Relations Division: Phone: +81-3-3580-8950

Information in the press releases is current on the date of the press announcement, but is subject to change without prior notice.