Investigations of SAW delay lines on c-plane AlN/sapphire at elevated temperatures

Aluminum nitride (AlN) on sapphire is a promising substrate for SAW (surface acoustic wave) sensors operating at high temperatures and high frequencies. To get an experimental measure of the suitability and temperature stability of such devices, several samples of SAW delay lines were fabricated on 2" c-plane (0001) sapphire substrates with 1 μm c-plane AlN layer on top. Time- and frequency responses were recorded during annealing treatments at temperatures up to 850°C and the signals were analyzed afterwards.