Solid-state power at microwave frequencies once meant gallium arsenide (GaAs) device technology. But in recent years, the high power density of gallium nitride (GaN) device technology has made it appealing to many designers, both for switching power supplies and high-power RF/microwave amplifiers. Although GaN technology still cannot reach to millimeter-wave frequencies in the manner of GaAs discrete devices and integrated circuits (ICs), it has proven to be a reliable performer at RF and lower microwave frequencies.

One of the leading suppliers of GaN devices, Ni-tronex (www.nitronex.com), recently announced that it had shipped more than 500,000 production GaN devices since introducing its first production-qualified products in 2006. The company began volume production of the devices (see figure) in 2009 for a variety of different packaged devices for power-supply, motor-drive, and RF/microwave amplification applications. The ISO-9001 certified manufacturer supports a variety of markets, including defense, commercial communications, industrial, and scientific areas. The company, which has been awarded 24 patents with 15 others pending, fabricates its GaN devices on standard silicon substrates, using a patented GaN-on-silicon process called the SIGANTIC® process.

“Shipping more than 500,000 devices is a testament to the early successes we’ve had in military communications, jammers, and cable TV infrastructure,” says Charlie Shalvoy, President and CEO of Nitronex. “We look forward to continued growth by expanding into emerging GaN markets such as radar, and eventually commercial wireless infrastructure.”

Efficient Power Conversion (www.epc-co.com) has developed enhancement-mode GaN-on-silicon transistors for power-management applications as an alternative to silicon power MOSFET devices. The firm’s model EPC1001 GaN field-effect transistor operates with 100-V drain-to-source voltage and 25 A current with low 5.6 mÙ drain-to-source resistance. They are ideal for use in DC/DC power conversion and in light-emitting-diode (LED) driver circuits and are relatively low in cost, produced on 150-mm silicon wafers in a standard silicon CMOS semiconductor foundry.

The company’s technology received a huge vote of confidence earlier this year when semiconductor giant Microsemi Corp. (www.microsemi.com) announced that they were working with Efficient Power Conversion on the development of enhancement-mode GaN FETs for high-reliability space and military applications. Microsemi plans to offer devices for voltages of 40, 60, 100, 150, and 200 V. The rugged devices are claimed to offer excellent high-temperature performance, with maximum junction temperature ratings approaching +300°C. The firm will offer devices in a variety of packages, including standard through-hole and surface-mount packages in addition to flip chip die. Preliminary testing has shown the devices to have excellent performance in high-radiation environments, with good single-event-effect (SEE) and total-ionizing-dose (TID) capabilities, making them particularly well suited for high-orbit and deep-space applications.

Last year, Panasonic (www.panasonic.com) revealed that it was investigating the use of GaN technology at even higher frequencies, and had developed a GaN-on-silicon device capable of 10.7 W output power at 25 GHz. The firm claims that the device has a power density of 2.4 W/mm at 60 GHz, which would be the highest reported power density for a GaN device at that frequency. The device features a metal-insulator-semiconductor (MIS) gate structure with crystalline silicon-nitride (SiN) film as gate insulator.

Any update on GaN device technology would be incomplete without a mention of TriQuint Semiconductor (www.triquint.com), selected last May to supply GaN power-transistor modules unmanned aerial vehicles (UAVs) for use by the US Air Force. The firm has participated in DARPA’s Wide Bandgap Semiconductor Technology Initiative (WBGS-RF) in pursuit of continued improvement of the technology for military applications.