High-performance robust ScN <i> _x </i> /Nb/ScN _<i>x</i> heaters for an integrated silicon nitride low-loss photonic platform

Silicon nitride is one of the most promising and mature integrated photonics platforms, providing a gateway to the development of cutting-edge devices based on photonic integrated circuits (PICs) with enhanced performance capabilities. For a wide range of applications, integrated heaters remain the preferred method for controlling PICs through the thermo-optic effect. Here, we demonstrate in detail the fabrication process and the characterization of heaters based on a ${\mathrm{Sc}\mathrm{N}}_{x}$/${\mathrm{Nb}/\mathrm{Sc}\mathrm{N}}_{x}$ stack. The proposed approach addresses both of the main issues that cause heater failures: electromigration and oxidation (oxygen diffusion). The findings of the experimental investigation suggest that the proposed ${\mathrm{Sc}\mathrm{N}}_{x}$/${\mathrm{Nb}/\mathrm{Sc}\mathrm{N}}_{x}$ heaters exhibit a critical current density ${j}_{c}\ensuremath{\sim}100\phantom{\rule{0.2em}{0ex}}{\mathrm{GA}/\mathrm{m}}^{2}$ and are capable of heating silicon nitride waveguides by more than $200{\phantom{\rule{0.1em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$, providing a specific optical path change per heater length $\mathrm{\ensuremath{\Delta}}{L}_{\mathrm{optical}}/{L}_{\mathrm{heater}}\ensuremath{\sim}5\phantom{\rule{0.2em}{0ex}}\text{\ensuremath{\mu}}\mathrm{m}/\mathrm{mm}$ for silicon nitride waveguides in the C band. Thanks to the elevated reliability level and remarkably high efficiency, the proposed ${\mathrm{Sc}\mathrm{N}}_{x}$/${\mathrm{Nb}/\mathrm{Sc}\mathrm{N}}_{x}$ heaters potentially enable a significant reduction in the PIC footprint, without compromising performance and robustness. Additionally, we carried out a rough experimental assessment of the magnitude of thermal crosstalk.