AFRL Lab Features New MBE Specifically for Gallium Oxide Power Devices

March 25, 2019 by Scott McMahan

The Oxide Molecular Beam Epitaxy laboratory at Wright-Patterson Air Force Base in Ohio, a U.S. Air Force Research Lab (AFRL) is equipped to become a dominant developer of high-quality semiconductor materials that could be the basis for a new class of lighter, smaller, more flexible electronics.

The new laboratory now has a specialized MBE chamber, a first-of-its-kind system designed specifically to grow gallium oxide. Dr. Shin Mou shows off the laboratory's new, specialized MBE chamber in the image above (photo courtesy of U.S. Air Force/Adrienne Kreighbaum). This unique piece of equipment enables the growth of semiconducting materials that can be used for specialized power electronics that are common in modern aircraft, as well as many consumer electronics devices.

"This is the first system of this kind specifically designed to grow gallium oxide, which is a promising new material for high-performance electronics," said Materials Research Engineer Dr. Don Dorsey.

Dorsey noted that while gallium oxide is not a new material, the recent discovery of some of its properties have made it an emerging electronic material. However, much remains to be learned about its properties and performance.

Gallium oxide can handle much higher operating voltages than commonly-used silicon-based semiconductors. As a result, it can be used effectively for high-power, high-voltage applications.

For aircraft electronics, components that are necessarily big and bulky could be made much smaller and lighter. Dorsey likens such size reductions to what happened with today's common laptop voltage converters.

"A simple example is the power adaptor located on the cords of laptop computers. We think the promise of this is that you could get rid of that entirely and have a small component on the circuit board that would do the same job." Dorsey explained that the AFRL team's work is geared toward similarly reducing the weight and size of Air Force systems.

Uniquely the Oxide MBE system is specifically and solely designed for the growth of gallium oxide. As Dorsey explained, contamination is a critical issue in the growth of quality crystals. Since the new MBE chamber will only grow gallium oxide, cross-contamination that could degrade the material quality will not occur.

"This unique piece of equipment gives us an advantage," said Dorsey. "We are able to produce extremely pure samples and have the assurance that our material formulations are exactly as we intend them."

The MBE capability lets AFRL materials experts to produce high-quality semiconducting materials and further refine their production capabilities through a synergistic relationship with AFRL sensors researchers, who incorporate the materials into their electronic components.

Feedback and Academic Research Aid Material Development

The sensors experts then offer feedback to the materials team, who use that information to adjust the material growth within the MBE chamber. This back-and-forth process feedback is helping the team learn more about the formulations that produce the best quality semiconductors for application-specific purposes.

According to AFRL materials researcher Dr. Shin Mou, the MBE Laboratory also equips AFRL to bridge the gap between university and industry research efforts. "The capability to produce up to four-inch wafers enables us to work with university Centers of Excellence as well as industrial research organizations to advance the material capabilities and open new doors for this technology."

He explained that AFRL will be able to pull findings from the research conducted within academia and put this improved understanding into action to further develop wafer-scale materials, and transfer the knowledge to industry partners for commercialization.

Mou explained that the long-term goals for this work include refining the material to the point that it can transferred to U.S. industry for large scale production.

Furthermore, having a domestic supply chain for these advanced semiconductors would ensure widespread, low-cost availability of these materials for both military and commercial use.

Cornell Partnering with AFRL at New Center for Excellence

The recent opening of the AFRL-Cornell Center for Epitaxial SolutionS, or ACCESS was an important immediate step for the AFRL research team. This Center of Excellence, led by Cornell University in partnership with AFRL, will give Cornell faculty and students the chance to work closely with AFRL researchers and laboratories. The knowledge base that grows out of ACCESS will complement the ongoing AFRL efforts including the MBE research, leading to a greater breadth of knowledge and expertise.

"We are excited about this collaboration with the university community," said Air Force Office of Scientific Research Program Officer, Dr. Ali Sayir. "The Centers of Excellence provide a means by which we can facilitate and draw from student and faculty research, while at the same time introduce students to the AFRL community and potential professional opportunities within. This Center is aligned well with the AFOSR mission and investment strategy on ultra-wide band gap materials funded through AFOSR core grants and Office of the Secretary of Defense investment on several Multi-Disciplinary University Research Initiatives."

"This is a very exciting time in the evolution of this technology," said Dorsey of the new MBE lab and university partnership. "These are major enablers for the advancement of these capabilities. The work we're doing will be a major step toward a new breed of high-power electronics to better enable the warfighter for tomorrow's challenges."