  Scandium-doped aluminum nitride (AlScN) with an asymmetric hexagonal wurtzite
structure exhibits enhanced second-order nonlinear and piezoelectric properties
compared to aluminum nitride (AlN), while maintaining a relatively large
bandgap. It provides a promising platform for photonic integration and
facilitates the seamless integration of passive and active functional devices.
Here, we present the design, fabrication, and characterization of AlScN EO
micro-ring modulators, introducing active functionalities to the chip-scale
AlScN platform. These waveguide-integrated EO modulators employ sputtered AlScN
thin films as the light-guiding medium, and the entire fabrication process is
compatible with complementary metal oxide semiconductor (CMOS) technology. We
characterize the high-frequency performance of an AlScN modulator for the first
time, extracting a maximum in-device effective EO coefficient of 2.86 pm/V at
12 GHz. The devices show a minimum half-wave voltage-length product of 3.12
V*cm and a 3-dB modulation bandwidth of approximately 22 GHz. Our work provides
a promising modulation scheme for cost-effective silicon-integrated photonics
systems.
