ABSTRACT We present a monolithically integrated single‐layer Hf 0.5 Zr 0.5 O 2 (HZO) in‐plane phase shifter on a Si 3 N 4 ring resonator, enabling electrically programmed, nonvolatile resonance shifts. The lateral TiN–HZO–TiN electrode geometry produces a measurable resonance shift with an onset near 140 V and stable programmed states up to 200 V. Four‐dimensional scanning transmission electron microscopy (4D‐STEM) analysis reveals voltage‐induced changes in both phase fractions and in‐plane residual strain retained after bias removal. First‐principles calculations incorporating the experimentally extracted strain values indicate that this strain leads to a decrease in the refractive index for all phases of HZO in the near‐infrared wavelength range. Moreover, the orthorhombic phase is found to exhibit the highest refractive index among the coexisting phases, such that the observed reduction in o‐phase fraction further contributes to the net decrease in the effective refractive index. These combined effects consistently explain the experimentally observed nonvolatile blueshift of the ring resonance and highlight electrically induced crystallographic reconfiguration in HZO as a viable mechanism for programmable photonic elements on the Si 3 N 4 platform.
Kong et al. (Wed,) studied this question.