Fabrication of aluminium nitride/diamond and gallium nitride/diamond SAW devices

Surface acoustic wave (SAW) devices have been fabricated from thin films of gallium nitride and aluminium nitride deposited on a range of chemical vapour deposition (CVD) diamond substrates. The growth of aluminium nitride and gallium nitride layers on diamond by chemical beam epitaxy (CBE) is reported for the first time. Triethyl gallium and ethyldimethylamine alane precursors were used in conjunction with nitrogen from an RF atom source to deposit the gallium nitride and aluminium nitride layers at substrate temperatures in the range 540 to 575 °C. These layers have been characterised by Raman spectroscopy and atomic force microscopy. The SAW structures were completed by the deposition of gold or aluminium interdigitated electrode structures on the as-deposited nitride surfaces. Preliminary testing indicates that these devices operate as bandpass filters with characteristics consistent with the propagation of acoustic waves at very high phase velocities within the nitride–diamond multi-layer substrate.