Wafer-scale hybrid molecular beam epitaxy of BaTiO3 and SrTiO3 on silicon

TL;DR

This paper demonstrates a scalable wafer-scale hybrid molecular beam epitaxy method for high-quality BaTiO3 films on silicon, enabling improved ferroelectric and electro-optic properties for integrated photonics.

Contribution

It introduces a fully hybrid MBE process for wafer-scale growth of BaTiO3 on silicon with superior crystallinity and electro-optic performance compared to pulsed laser deposition.

Findings

Achieved uniform BTO films on 4-inch Si wafers with growth rates over 75 nm/h.

BTO films grown by hMBE show larger effective EO coefficient (248 pm/V) than PLD-grown films.

The hMBE-grown BTO exhibits superior crystallinity and a sharp BTO/STO interface.

Abstract

The integration of epitaxial barium titanate (BTO) on silicon represents a highly promising pathway for next-generation, energy-efficient photonic integrated circuits due to BTO's exceptionally high Pockels coefficients. However, the scalable epitaxy of BTO on Si remains hindered by complex stoichiometric control and slow growth rates. In this work, we demonstrate the continuous, uniform wafer-scale growth of high-quality BTO films on SrTiO3 (STO)-buffered 4-inch Si(001) wafers using a fully hybrid molecular beam epitaxy (hMBE) approach. By utilizing titanium tetraisopropoxide as a titanium precursor, we achieve a self-regulating, adsorption-controlled layer-by-layer growth at rates exceeding 75 nm/h, while maintaining an atomically sharp and structurally coherent BTO/STO interface. We systematically compare the structural, ferroelectric, and electro-optic (EO) properties of fully hMBE-grown BTO with those deposited via pulsed laser deposition (PLD) on identical STO/Si templates. While both techniques yield high-quality c-domain dominated films, the optimized hMBE-grown BTO exhibits superior crystallinity and a larger effective EO coefficient of 248 pm/V, surpassing that of the PLD-grown films (220 pm/V). These results highlight the advantages of the fully hMBE approach as a scalable, deterministic, and high-performance materials platform for wafer-scale integrated ferroelectric photonics.