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GaN Power FET achieves 65.4W in Ku-band

Posted: 12 Oct 2007 ?? ?Print Version ?Bookmark and Share

Keywords:power field effect transistor? GaN power FET? Ku-band?

Ku-band power FET

Toshiba Corp. has developed a gallium nitride (GaN) power FET for the Ku-band (12-18GHz) frequency range that achieves an output power of 65.4W at 14.5GHz, said to be the highest level of performance at this frequency band today. The main application of the new transistor will be in base stations for satellite microwave communications, which carry high-capacity signals, including high-definition broadcasts.

Advances in Ku-band microwave amplifiers focus on replacing the electron tubes conventionally used at this bandwidth with semiconductors, particularly GaN devices, which offer advantageous high power characteristics at higher microwave frequencies.

The new power FET has a high electron mobility transistor (HEMT) structure that Toshiba has optimized for the Ku-band. The company replaced source wire bonding with via hole technology to reduce parasitic inductance and also improve overall design of the matching circuit for practical application at Ku-band frequencies.

Device technology
Toshiba achieved the performance of the new FET by optimizing the composition and thickness of the AlGaN and GaN layers formed on the highly heat-conductive silicon carbide (SiC) substrate of the HEMT structure. To ensure high performance at Ku-band frequencies, Toshiba has applied a shorter gate length of below 0.3?m, and optimized the shape of each electrode and element configuration to enhance heat dissipation.

To reduce the parasitic inductance and improve higher frequency performance, Toshiba developed a unique technology for forming via holes, which pass from the surface source electrode through the chip to the ground. Success in forming via holes in SiC substrate, recognized as a highly demanding process, is a breakthrough in development of the new FET.

As gate lengths shorten, suppression of current leakage at the gate electrode is essential for achieving high level performance. A unique overcoat process applied around each gate electrode contributes to suppressing gate leakage to 1/30 that of Toshiba's conventional approaches. Electron beam exposure technology is applied in order to secure stable processing of gate lengths below 0.3?m.

Other key features include a linear gain of 8.2dB, saturation power of 65.4W, drain voltage of 30V and operating frequency of 14.5GHz. The device has a chip size of 3.4mm x0.53mm and measures 21mm x 12.9mm when packaged.

Sample shipment of the new power FET will begin by year-end, with mass production set to begin by March 2008.

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