In research published recently in Applied Physics Letters, the team describes their use of energetic neutral atom-beam lithography/epitaxy to grow crystalline and polycrystalline gallium nitride (GaN) films on bare c-axis-oriented sapphire at temperatures between 100 and 500 degrees Celsius using low kinetic energy nitrogen atoms and a simultaneous flux of gallium metal.
Energetic neutral atom-beam lithography, or ENABLE, is a Los Alamos system that produces a beam of neutral atoms with low kinetic energies that can be used for various kinds of specialized surface chemistry at near room temperatures, often producing results that are unattainable using other techniques. Epitaxy is the process of growing one crystal layer of a material of another crystalline substance.
According to Mark Hoffbauer, the principal investigator for the GaN ENABLE project, "the beauty of using ENABLE for growing crystalline gallium nitride films is that normally the process requires substrate temperatures of 900 to 1,100 degrees Celsius and extremely harsh, reactive environments. Those conditions eliminate a lot of useful materials as substrates because they would melt or be degraded at the higher temperatures. Our lower temperature technique has the potential to allow gallium nitride films to be grown on many more types of inexpensive substrate materials, including glass and certain polymers."
Another researcher on the team, Alex Mueller adds, "The low temperatures employed by ENABLE allow for the incorporation of electronic and magnetic dopants into the films while simultaneously avoiding phase segregation and clustering problems that are limiting the widespread use of these materials in other applications. The fact that there are no impurities inherent in the ENABLE process make defect and impurity free films possible, thereby simplifying device fabrication."
The research is supported by the Los Alamos Laboratory-Directed Research and Development funding.
Los Alamos National Laboratory, a multidisciplinary research institution engaged in strategic science on behalf of national security, is operated by Los Alamos National Security, LLC, a team composed of Bechtel National, the University of California, The Babcock & Wilcox Company, and Washington Group International for the Department of Energy's National Nuclear Security Administration.
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