Electro-optic response in epitaxially stabilized orthorhombic <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>m</mml:mi><mml:mi>m</mml:mi><mml:mn>2</mml:mn></mml:mrow><mml:mo> </mml:mo><mml:mrow><mml:mi>BaTi</mml:mi><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math>
Marc Reynaud, Pei‐Yu Chen, Wente Li, Therese Paoletta, Sunah Kwon, Daehun Lee, Ilya Beskin, Agham Posadas, Moon J. Kim, Chad M. Landis, Keji Lai, John G. Ekerdt, Alexander A. Demkov
Abstract
$\mathrm{BaTi}{\mathrm{O}}_{3}$ (BTO) is an emergent material in the field of silicon-integrated photonics, as its thin films have been demonstrated to have a very large electro-optic (Pockels) coefficient that can be used for optical modulators. However, BTO grown directly on $\mathrm{SrTi}{\mathrm{O}}_{3}$ (STO)-buffered Si (STO is required for epitaxial growth) initially grows with a polarization direction not suitable for the geometries currently used in photonic devices. Here, we grow BTO on a $\mathrm{BaSn}{\mathrm{O}}_{3}$-buffered STO substrate to form orthorhombic $mm2$ BTO, which has in-plane polarization orientation needed for photonic devices. Extensive crystalline characterization is done to confirm the high quality of the films, along with electro-optic measurements. Theoretical simulations coupled with the experimental results provide a foundational understanding of the properties of strain-stabilized orthorhombic BTO. Large electro-optic coefficients of 121 pm/V are observed in films as thin as 40 nm.