Active Silicon Integrated Nanophotonics: Ferroelectric BaTiO₃ Devices

Abstract

The integration of complex oxides on silicon presents opportunities to extend and enhance silicon technology with novel electronic, magnetic, and photonic properties. Among these materials, barium titanate (BaTiO3) is a particularly strong ferroelectric perovskite oxide with attractive dielectric and electro-optic properties. Here we demonstrate nanophotonic circuits incorporating ferroelectric BaTiO3 thin films on the ubiquitous silicon-on-insulator (SOI) platform. We grow epitaxial, single-crystalline BaTiO3 directly on SOI and engineer integrated waveguide structures that simultaneously confine light and an RF electric field in the BaTiO3 layer. Using on-chip photonic interferometers, we extract a large effective Pockels coefficient of 213 ± 49 pm/V, a value more than six times larger than found in commercial optical modulators based on lithium niobate. The monolithically integrated BaTiO3 optical modulators show modulation bandwidth in the gigahertz regime, which is promising for broadband applications.

Lanthanide-Assisted Deposition of Strongly Electro-optic PZT Thin Films on Silicon: Toward Integrated Active Nanophotonic Devices

“…However, recent works show advancements toward micro and nano scale EO devices on the silicon platform based on complex and costly layer bonding approaches 28 and with the more sophisticated epitaxially grown ferroelectric oxides. 10 In this work, we demonstrate a novel technique to realize textured PZT thin films on a variety of substrates such as bare silicon, glass (corning glass type CB90IN (Delta Technologies)), glass/ITO, Si/Al 2 24 The SrTiO 3 template layer results in epitaxial PZT thin films, but this growth technique is limited to crystalline substrates (Si), whereas in the latter technique the phase purity of the films critically depends on the SiO 2 thickness. The possibility of chemical reaction at the PZT/SiO 2 /Si interface at high temperature has also not been discussed there.…”

High ferroelectric polarization in c-oriented BaTiO3 epitaxial thin films on SrTiO3/Si(001)

“…[1][2][3][4] For example, a-oriented BTO on silicon has permitted integrating optical devices with improved properties respect the commonly used LiNbO 3 . 5,6 On the other hand, c-oriented BTO has been used to fabricate memory devices on silicon as ferroelectric tunnel junctions. 7,8 In memory devices high switchable ferroelectric polarization along the outof-plane direction is desired.…”

“…9,10 Moreover, the growth of epitaxial BTO on Si(001) requires a buffer layer, being used either yttria-stabilized zirconia (YSZ) and/or LaNiO 3 (LNO), [11][12][13][14][15] or SrTiO 3 (STO). [5][6][7][8][16][17][18][19][20][21] The YSZ buffer layer is combined with other layers to accommodate progressively the high lattice mismatch of around 9% with BTO. The high mismatch causes in-plane compressive epitaxial stress, favoring growth of c-oriented BTO with high ferroelectric polarization for a broad range of BTO thickness.…”

Development of new photonic devices based on barium titanate in silicon

“…Furthermore, the potential of growing high-quality thin film crystalline layers of BTO on strontium titanate (SrTiO3) templated silicon and silicon on insulator (SOI) substrates [12,49,50] has recently opened a path towards the development of hybrid BTO silicon EO modulators with disruptive performance [51][52][53][54][55][56]. Table 1.1 summarizes the BaTiO3 properties at 1550nm optical wavelength and the enhanced capabilities offered to the silicon platform.…”

“…Furthermore, they also demonstrate the presence of ferroelectricity in the BTO film opening the way for enabling breakthrough photonic functionalities by exploiting the EO bistable effect. Another group of Yale university (USA) has been able to integrate BaTiO3 based Mach-Zehnder and ring modulators on SOI using a slot waveguide structure [49]. They extracted an effective Pockels coefficient of 213 +/-49 pm/V, and demonstrated 4.9 GHz operation with a Vπ·L of 1 V.cm.…”