Doped Silicon Temperature Compensation of Surface Acoustic Wave Devices

One of the critical performance parameters of surface acoustic wave (SAW) devices for frequency references and sensors is the temperature coefficient of frequency (TCF). Although aluminum nitride (AIN) and scandium-doped AlN (ScAlN) are attractive piezoelectric materials, the TCFs of AIN-based resonators are still relatively high. Here, doped silicon is employed as the temperature compensating material while a thin-film piezoelectric ScAIN is employed for actuation. SAW resonators with various in-plane orientations are designed, fabricated, and characterized under different temperatures. Zero TCF is realized in the SAW resonator arranged at around 75° from the <;100> direction of the (110) doped silicon wafer, demonstrating promising passive temperature compensation.