Ultrasonic Microspectroscopy of Wide Bandgap Semiconductor Materials

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To realize highly efficient and long life devices using wide bandgap semiconductors, such as AlN, ZnO, SiC, and GaN, it is necessary to employ homogeneous bulk single crystal substrates as well as proper fabrication processes for making homogeneous and high-quality films. To do so, we developed a new method for evaluating semiconductor materials using ultrasonic micro-spectroscopy (UMS) technology as an accurate evaluation technology. Although characterization of epitaxial film is generally difficult because of their elastic anisotropy, we demonstrated usefulness of the evaluation method through measuring velocities of leaky surface acoustic waves by the UMS technology and measuring density based on the Archimedes' principle for Sc doped AlN film specimens.