Fig 1: Gallium nitride (GaN)-based transistor

The transistor was formed on a silicon (Si) substrate, which can be easily mass-produced and is available in large diameters. The company claims that the transistor has more output power than any other GaN-based transistors in the industry.

Furthermore, at 60GHz, the output power density of the transistor is as high as 2.4W/mm, which is even higher than that of a GaN-based transistor formed on a silicon carbide (SiC) substrate, Panasonic said.

Fig 1: The gallium nitride (GaN)-based transistor that has a high output of 10.7W in a millimeter waveband of 25GHz

This time, Panasonic prototyped a 25GHz transceiver whose modulation method is OFDM (orthogonal frequency division multiplexing) and achieved an average output power of 2W with an effective data transfer rate of 16Mbps. According to an estimate based on the gain of the transceiving antenna and transmission loss in the atmosphere, the transceiver is capable of long range communication of 84km, the company said.

The high output of the GaN-based transistor was realized by the following two improvements. First, Panasonic improved the crystallinity of a GaN film formed on a Si Substrate so that it becomes possible to apply a large drain current of 1.1A/mm.

Second, the company increased the drain voltage. The newly-developed GaN-based transistor is an MIS (metal insulator semiconductor) type. Its resistance to gate destruction was enhanced by using a high-crystallinity silicon nitride (SiN) film, instead of an amorphous SiN film, as a gate insulating film of the transistor. As a result, a drain voltage of +55V was realized.