By Rear Admiral Matthew L. Klunder
Chief of Naval Research
Gallium nitride (GaN) is one of the most important compounds you’ve probably never heard of. If you have a Blu-ray disc player in your house, you already own some gallium nitride. If you have a flat-screen LED television, that also has gallium nitride. Quite simply, without this material, much of today’s high-end electronics wouldn’t exist. You may also be interested to know some of the first investments in early research for GaN began in 1969 at the Office of Naval Research.
Gallium itself does not exist in pure form in nature. As a compound, however, when combined with nitrogen, gallium produces an extremely useful semiconductor for a wide range of electronics.
Late last year, the Navy signed a contract with Raytheon to produce the next generation of high-powered radar, the Air and Missile Defense Radar (AMDR). This radar will be the centerpiece of the combat system of the DDG-51 Flight III destroyer—and its circuits are built with gallium nitride semiconductors. Just like with your Blue Ray player, GaN makes this important new radar technology possible.
Getting to the point of making GaN into a useable material—for the Navy or the commercial world—took nearly 30 years of hard work by researchers in multiple countries, numerous wrong turns, and a tremendous amount of patience. And it all happened with the help of U.S. naval research.
In the 1960s, the electronics on Navy surface ships and submarines were dominated by vacuum tube technology. It was affordable, but bulky. Most important, vacuum tubes had power limitations that were soon reached in the explosion of new devices and systems that appeared in that decade. Solid-state electronics—made with many materials of which GaN is only one—offered a real solution, but they were expensive, barely tested, and difficult to manufacture. Nonetheless, the potential payoffs from success were so great that there were people willing to do the research—and pay for it.
In 1969-70, Max Yoder, a program manager with ONR, provided some of the first funding for early research on gallium nitride at RCA Laboratories near Princeton, N.J. He was taking a long-term perspective not on what was, but what might be. What makes GaN special is that electrons move more quickly within it—meaning that devices containing it can sustain voltages and temperatures higher than other solid-state semiconductors. (This is the quality most desired by the Navy for new radars and other electronics.) In addition, GaN is the only compound that creates blue-green light for lasers or LEDs. Blue light can be tuned to a smaller area of, say, a DVD, allowing more data to be stored on a disk (which is why Blue Ray discs are the same size as DVDs, but provide significantly more detailed video).
All of this potential was understood by many people even in the 1960s. The problem—first confronted by the researchers at RCA and by a generation of engineers and scientists since then—is that GaN is particularly difficult to produce in quantity and quality. Manufacturability was the central focus of all early research efforts, and RCA had success in creating some of the first GaN crystals. That work was expanded in the 1970s by researchers in Japan, who were especially interested in producing lighting using GaN. By the early 1990s, two competing groups would come out with the first mass-produced blue LEDs. Military interest in GaN then resumed as some of the issues associated with manufacturing were solved—to the point that GaN and similar semiconductors are now considered essential components of military-grade electronics. Some current GaN technologies that are planned for incorporation into the fleet include several radar and communications projects, such as components in the Next-Generation Jammer (NGJ) that will go on the F-35B Lightning II and in the Marine Corps’ Ground/Air Task Oriented Radar (G/ATOR).
The Road Ahead Depends on the Road Behind
Gallium nitride’s circuitous journey illustrates some common themes of our discoveries—large and small—on their pathways from inception to functional technology. First, basic research demands patience and the willingness to take risks. Many people knew the potential of GaN, but what was needed was someone willing to assume the initial heavy lifting needed to get past the material’s primary limitations. Second, basic research depends on an open and collaborative environment. Productive GaN research required the efforts of engineers and scientists on several continents, a sign of the great power of cooperation in today’s globalized world. Third, there is an intimate relationship between military and civilian research. From aviation to computers to a host of other technologies we now take for granted, many of the tools of modern life began within the crucible of the civil-military relationship.
Managing that relationship is the job of U.S. naval research, whether it’s ONR or the labs, warfare centers, system commands, universities, or industry partners of the Naval Research Enterprise. Our mission every day is to think about the ways in which the basic research of today can be turned into the technology that helps save the lives, fight the wars, and maintain the peace of tomorrow.