Fig. 2: Fabrication and characterization of ScAlN photonics.
From: Unveiling the Pockels coefficient of ferroelectric nitride ScAlN
a Preparation of ScAlN-on-insulator platform. HSQ-assisted flip-chip bonding is employed to transfer ScAlN thin film from a metallic substrate onto an insulator-on-Si carrier wafer. The growth substrate is subsequently removed through lapping, polishing, and selective etching procedures. b AFM scanning of the surface morphology of polished ScAlN surface, indicating very low surface roughness (Ra = 0.21 nm). c Cross-sectional SEM image of bonded ScAlN-on-insulator substrate. The Si and AlN buffer layers of the original substrate have been selectively removed, leaving a thin layer of Mo atop ScAlN thin film. No voids are present between the spin-coated HSQ layers, indicating excellent bonding quality. d False-color SEM image showing a fraction of an uncoated ScAlN ring resonator. A smooth sidewall is yielded with our dedicated etching recipe. e Transmission spectrum of a typical Sc0.1Al0.9N ring resonator. A linewidth of 15 pm is observed, which corresponds to a loaded quality factor of QL = 1.0 × 105.
