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Toshiba touts power output of GaN-based FET

Posted: 14 Sep 2005 ?? ?Print Version ?Bookmark and Share

Keywords:microwave communications? fet? transistor? gaas? fet?

Toshiba Corp. has developed a gallium nitride (GaN) based power field effect transistor that it says far surpasses the operating performance of the gallium arsenide FET widely used in base stations for terrestrial and satellite microwave communications.

The company claims output power of 174W at 6GHz from the transistor, the highest level of performance reported at this frequency. Typical GaAs based FETs manage output power of 90W at 6GHz and 30W at 14GHz.

Toshiba says the performance was achieved through optimizing the epitaxial layer and chip structures for 6GHz-band operation and by adopting a four-chip combination structure to minimize heat build-up.

The company expects to have samples of the device next year, and suggests the techniques it is using could yield even higher output levels.

Full details of the GaN power FET and its technology are being presented at the International Conference on Solid State Devices and Materials that is being held between September 12 to 15 in Kobe, Japan.

The paper being presented notes that heat dissipation is a critical issue with GaAs, to the point that the material is fast approaching the upper limits of its performance characteristics.

The Toshiba researchers say GaN shows great promise for application in amplifiers that support higher frequencies than the microwave band, since it offers higher saturation electron velocity, higher dielectric breakdown voltage and a higher operating temperature range than GaAs.

The newly developed surface treatment process and heat treatment technology used led to very low contact resistance at the source and drain electrodes, allowing maximization of the GaN material characteristics. A novel gate electrode structure also contributed to reduction of the gate leakage current to 1/30 of that achieved with existing techniques.

Toshiba says that while electron beam exposure technology has been generally used in a lithography process for GaN power FET in the C band and higher frequencies, the stepper exposure that it has used for this FET is also better suited for mass production.

- John Walko

EE Times

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