A report describes research on thin oxide films intended for use as variable-high-permittivity dielectrics in advanced tunable capacitors and on thin nitride films as starting materials for advanced high-electron- mobility transistors (HEMTs). In this research, a custom molecular-beam-epitaxy system was used to grow thin films of TiO2, SrTiO3, Ba1-xSrxTiO3, MgO, and AlxGa1-xN (where 0 ≤ x ≤ 1). Growth parameters and properties of the films were investigated with a view toward developing processes for fabricating HEMTs using epitaxy of AlxGa1-xN, processes for fabricating varactors using epitaxy of Ba1-xSrxTiO3, and processes in which integration of Ba1-xSrxTiO3 onto AlxGa1-xN templates would be facilitated by use of MgO buffer layers. The films were characterized, variously, in situ by reflected-high-energy-electron diffraction, source-flux monitoring, and/or residual-gas analysis. The films were characterized, variously, ex situ by atomic-force microscopy, x-ray rocking-curve measurements, high-resolution x-ray diffraction, Rutherford backscattering, cross-section transmission electron microscopy and diffraction, and/or radio-frequency-loss metrology. In addition, the AlxGa1-xN films were characterized in situ by multi-beam optical stress-sensor analysis.
This work was done by Volker D. Heydemann, Lance Haney, Mike Lanagan, Matthew Snyder, Joan Redwing, Xiaojun Weng, Dan Perez, Jeremy Acord, and Jian Xu of Pennsylvania State University; and Marek Skowronski, Paul Salvador, and Patrick Fisher of Carnegie Mellon University for the Office of Naval Research.
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Oxide and Nitride Films for Tunable Capacitors and HEMTs
(reference ONR-0003) is currently available for download from the TSP library.
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