Oki develops high-performance GaN-on-SiC HEMT
To improve the amplification characteristics of the (Al)GaN-on-SiC device, Oki successfully fabricated T-shaped recessed gates, reduced the gate length, and optimized the device structure. The transistor achieved high frequency performance including a maximum oscillation frequency (fmax) of 126 GHz and a current gain cut-off frequency (ft) of 67 GHz.
To achieve high power output using a conventional I-shaped gate, the gate must be made wider and longer, increasing its resistance and decreasing the operation frequency. A T-shaped gate electrode provides a larger cross-section and consequently a lower electrode resistance.
The use of a recessed gate dramatically reduces the parasitic resistance of the transistor, while improving amplification and high frequency characteristics. It requires very difficult, high-precision fabrication techniques rarely applied to GaN HEMTs.
The transistor reduces the power consumption and space required for wireless communications systems in mobile-phone basestations and wireless LANs. Oki developed the transistor in partnership with Professor Takashi Egawa at the Research Center for Micro-Structure Devices at the Nagoya Institute of Technology.
"This development marks a critical step toward broadening the applicability of this type of transistor, which we at Oki expect to be an essential device in the next generation of wireless communications systems," said Harushige Sugimoto, General Manager of the Corporate R&D Center at Oki Electric. "I believe this record high transconductance results from our sustained R&D dedication to innovative technologies."
The rapid increase of channels made necessary by growing communications volumes has increased the need to reduce power consumption and space per channel of mobile phone basestations and other wireless communications systems. With its improved amplification characteristics, Oki s new power transistor makes it possible to reduce the number of amplifier stages in transceiver equipment, providing precise response to this market demand.
Oki intends to further enhance the performance of the GaN-on-SiC HEMTs by increasing power output and reducing costs. The device will be commercialized for mobile-phone basestations and wireless LANs, and Oki plans to begin sample shipments in the second half of the fiscal year ending March 31, 2004.
Technology development was undertaken as an Ultra-Low-Loss Power Device Technologies project by Ministry of Economy, Trade and Industry (METI) under the auspices of the R&D Association for Future Electron Devices (FED) supported by New Energy and Industrial Technology Development (NEDO).
