The authors report on the fabrication, piezoresistive readout, and frequency response of doubly clamped c-axis gallium nitridenanowire (NW) resonators that show mechanical quality factors exceeding 10 000. The devices are fabricated using a combination of lithographic patterning and dielectrophoresis to suspend NWs across 10 μm gaps. An electrostatic gate induces NW vibration, which is electronically detected via NW piezoresistance. The naturally occurring range of NW diameters results in lowest beam resonances in the range of 9–36 MHz, consistent with a Young’s modulus of roughly 300 GPa. Mechanical quality factors, Q, as high as 26 000 under vacuum at 8 K are observed. Selective variation of NW temperature by local joule heating while maintaining cold mechanical clamps demonstrates the dominant role of the polycrystalline metallic end clamps in the room-temperature mechanical dissipation.
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