Epitaxial Oxides on Glass: A Platform for Integrated Oxide Devices

Abstract

The fabrication of epitaxial, ultrathin SrTiO3 (STO) on thick SiO2 without the need for complicated wafer-bonding processes has been demonstrated. The resulting transition metal oxide (TMO)-on-glass layer stack is analogous to traditional silicon-on-insulator (SOI) wafers, where the crystalline device silicon layer of SOI has been replaced by a crystalline functional TMO layer. Fabrication starts with ultrathin body SOI on which crystalline STO is grown epitaxially by molecular beam epitaxy. The device silicon layer is subsequently fully oxidized by ex situ high-temperature dry O2 annealing, as confirmed by X-ray photoelectron spectroscopy, X-ray reflectivity, and high-resolution electron microscopy. STO maintains its epitaxial registry to the carrier silicon substrate after annealing, and no evidence for degradation of the STO crystalline quality as a result of the TMO-on-glass fabrication process is observed. The ease of fabricating the TMO-on-glass platform without the need for wafer bonding will enable rapid progress in the development of state-of-the-art TMO-based electronic and photonic devices.

Monolithic Barium Titanate Modulators on Silicon-on-Insulator Substrates

“…The STO buffer was then grown in two steps: a 2 nm seed layer grown at 200 °C and crystallized at 550 °C, followed by an additional 3 nm of STO growth at 550 °C and 5 × 10 –7 Torr of molecular oxygen. After the STO deposition, a patented controlled subsurface oxidation of the device Si layer is performed to transform the Si into SiO 2 , which merges with the buried oxide layer of the SOI wafer without disrupting the overlying STO layer (crystal-on-glass technology). The BTO was then grown by off-axis RF sputtering from a stoichiometric ceramic target in a sputter deposition chamber connected via an ultra high vacuum (UHV) buffer to the MBE growth chamber .…”

Three-Dimensional Integration of Functional Oxides and Crystalline Silicon for Optical Neuromorphic Computing Using Nanometer-Scale Oxygen Scavenging Barriers

“…After degreasing, the substrates were cleaned with UV ozone for 30 min to remove organic contaminants. The substrates were then loaded into the MBE and the native oxide was removed via a Sr-assisted desorption process. , …”

“…The substrates were then loaded into the MBE and the native oxide was removed via a Srassisted desorption process. 63,64 The 10-unit cell STO buffer layer was deposited on the silicon substrate at a rate of approximately one monolayer (ML) per minute using the recrystallization process described in detail elsewhere. 64 A total of 50 unit cells of epitaxial LAO were subsequently deposited on the STO template by shuttered deposition of metallic La and Al in the presence of molecular oxygen.…”

Oxide‐Based Optoelectronics

“…[65] Further fabrication advancements, including integration of such epitaxial QWs onto thermally oxidized silicon via direct deposition and the 3D integration of crystalline silicon and epitaxial oxides, promise to bring a variety of oxide-based QW technologies, including infrared photodetectors, quantum cascade lasers, and EO modulators, closer to reality. [66,67]…”