From radar to jammers, the defence industry has spent more than a decade developing GaN for US military applications. Compound Semiconductor asks Raytheon, where next for the technology?

Raytheon air and defence missile radar comprises a GaN S-band radar, X-band radar and a radar suite controller. [Raytheon]

Late last month, Raytheon celebrated taking GaN development from fundamental materials research to the demonstration of its X-band GaN transmit/receive integrated multichannel modules. On the way, the US defence contractor has built an array of more and more complex GaN-based devices, including transistors, monolithic microwave integrated circuits and transmit/receive modules.

These systematic developments have spanned more than a decade of development, leading to better radar, electronic warfare, navigation and communications systems. In the words of Joe Smolko, director of Microelectronics, Raytheon IDS Advanced Technology Programs: "In the late 1990s Raytheon started experimenting with the first GaN transistors and then we made a decision back then to have a sustained and substantial investment in GaN so we partnered with government."

"GaN has had such clear advantages for high performance systems in terms of its power density, efficiency and cost benefits." he adds. "It really has become a pervasive technology that we have looked to implement in many emerging applications,"

Indeed, today the technology can be found in the company's air and missile defence radar (AMDR) and next generation jammers, which are being snapped up by US defence.

For example, Raytheon recently batted back entrenched competitors Lockheed Martin and Northrop Grumman to win a $380.7 million contract from the US Navy to develop S-band AMDR and radar suite controller, for its Flight III Arleigh Burke-class destroyer ships. The company's AMDR uses existing X-band horizon search radar and the latest S-band integrated AMDR designed for long-range detection of threats. The two radar are brought together through the radar suite, which coordinates the system.



A destroyer equipped with Raytheon’s Air and Missile Defense Radar leads a battle group in this artists’ rendition. [Raytheon]

This contract followed a similar US Navy contract, worth $279.4 million, in which Raytheon  is designing new tactical jammer systems for advanced electronics. The jammers will block enemy radar, communications and other RF systems, and again the company won the development contract over defence heavyweights, BAE, Northrop Grumman and ITT Exelis.

Crucially, both systems rely on Raytheon's GaN transmit/receive modules, which make up the transmitter of an active electronically scanned array radar, and are rapidly succeeding GaAs-based systems found in older generation radars. Given its back-to-back US Navy deals, beating established competition, Raytheon is clearly succeeding in its GaN research and development programs.

Proving manufacture

A crucial part of this development has been Raytheon's work with the US Air Force Research Laboratory's to put in place a 'low rate initial production" (LRIP) manufacturing process for its X-Band GaN MMICs. As part of the Department of Defense's 'Title III' program, this ensures the ICs have achieved a production capability defined as a manufacturing readiness level of 8; in other words, the ICs are ready to be inserted into defence systems.

Title III contracts have also been awarded to other key GaN players; TriQuint, Cree and Northrop Grumman, each to increase yield, lower cost and improve time-to-market cycles for defence and GaN integrated circuits.

Raytheon is the first to complete its Title III program - it started first - and during this time, the company has demonstrated its GaN MMIC manufacturing yields are in line with mature GaAs processes and has also cut costs by 76%.

Gene Himes, an AFRL program manager for the initiative is confident these projects will ensure the US retains a competitive edge in defence applications, as dominated by GaAs technologies, and ease the technology's entry to commercial applications.

"I don't know that GaN will ever supplant GaAs as many applications are well served by GaAs," he says. "However, by demonstrating improved manufacturability, the Title III contracts will eventually culminate in decreased cost... and will go a long way in terms of a transition to commercial applications."

But for Raytheon, the project's success gives the company manufacturing kudos. "Certainly MRL8 is a level of maturity that is consistent with us being able to insert it into all of our high performance military systems," says Smolko. "It shows a manufacturing maturity that is comparable or exceeds the tried and true GaAs, and really does give users the confidence to use it in crucial military applications."

So now this program is over, what next for Raytheon's GaN development? Right now  defence manufacturers, Lockheed Martin, Northrop Grumman and Raytheon, eagerly await the US Air Force's final decision on its latest multi-million dollar contract, to develop Three Dimensional Expeditionary Long Range Radar (3DELRR).

Designed to replace the decades-old TPS-75 radar system, this ground-based radar will detect, identify and track enemy aircraft, missiles and drones. Raytheon's system is a C-band radar, again based on GaN, and as Smolko says: "We continue to carry out research and development into GaN... our current microwave process is still finding pervasive applications in many systems - some I just can't get into - but beyond this we're extending it to work at higher frequencies."

"You know, we will continue to mature this technology and eke out the last bit of performance cost benefit out of it," he adds