CMOS-compatible photonic integrated circuits on thin-film ScAlN

Abstract

Scandium aluminum nitride (ScAlN) has recently emerged as an attractive material for integrated photonics due to its favorable nonlinear optical properties and compatibility with complementary metal-oxide semiconductor (CMOS) fabrication. Despite the promising and versatile material properties, it is still an outstanding challenge to realize low-loss photonic circuits on thin-film ScAlN-on-insulator wafers. Here, we present a systematic study on the material quality of sputtered thin-film Sc0.1Al0.9N produced in a CMOS-compatible 200 mm line, including its crystallinity, roughness, and second-order optical nonlinearity, and developed an optimized fabrication process to yield 400 nm thick, fully etched waveguides. With surface polishing and annealing, we achieve micro-ring resonators with an intrinsic quality factor as high as 1.47 × 105, corresponding to a propagation loss of 2.4 dB/cm. These results serve as a critical step toward developing future large-scale, low-loss photonic integrated circuits based on ScAlN.