Photonic van der Waals integration of functional nanomembranes towards multifunctional heterogeneous photonic integrated circuits

Nontechnical Description:

Information technology has established itself as the cornerstone of modern society, underpinned by sophisticated semiconductor hardware with various functionality. To address the electrical bottleneck in integrated electronics, photonics-based scenarios have showcased unprecedented strengths in broadband, high-speed, and low-loss information processing and communications.

However, conventional strategies relying on single material platforms encounter varying limitations in device performance and multifunctionality from their fundamental material shortcomings. A versatile platform for heterogeneous integration of different functional optical materials is not only a driving engine to prototype novel high-performance integrated photonic applications for information society, but also essential to investigate diverse nanophotonic physics such as the interplay between electromagnetic waves and other physical fields.

We here propose the photonic van der Waals (vdW) integration on a library of distinct functional materials to infuse novel device functionalities established photonic platforms that were previously impossible to realize via single optical material. This includes the vdW integration of electro-optical (EO) material (barium titanate, BTO), cobalt ferrite (CFO), and III-V thin films (GaN) as gain or piezoelectric materials to Si and SiN photonics for high-performance and multifunctional integrated photonic circuits, providing a new paradigm for novel hetero-integration strategy to advance semiconductor technology, and explore nanoscale photonic phenomena such as Pockels EO modulation, mechanical-optical effects, lasing, and nonlinear physics.

Technical Description:

The hetero-integration of different optical materials, in contrast, can inspire record-setting devices and offer richer design freedom. Conventional hetero-integration approaches rely on hetero-epitaxy, limited by rigorous lattice matching and processing compatibility constraints. The photonic vdW integration thus permits versatile hetero-integration of diverse nanomembranes for vast applications with 3 significant breakthroughs: (1) Proposed layer transfer technique enables the vdW integration of dissimilar single-crystalline functional materials to arbitrary prefabricated photonic templates with excellent quality, which is previously not achievable via conventional heteroepitaxy methods. (2) The vdW integration concept is further extended to handling novel 3D materials for constructing novel vdW integrated photonic layouts to study nanophotonic coupling between light and other physical fields. (3) A universal platform to integrate multiple functional materials to a single photonic chip.

We plan to vdW integrate BTO, GaN, and cobalt ferrite to Si and silicon nitride (SiN) photonics to develop high-performance integrated EO modulators, on-chip photodetectors, and isolators, as well as multi-materials co-integrated photonic chip covering key functionalities of optical modulations and photodetections for optical communication applications. BTO and cobalt ferrite will be grown by pulsed laser deposition (PLD) for epitaxial lift-off.

Single-crystal GaN will be prepared by remote epitaxy via molecular beam epitaxy with 2D-materials-assisted layer transfer (2DLT) technique. Mach-Zehnder interferometers, ring resonators, and other dielectric waveguides structures will be fabricated in cleanroom for layer transfer. Optical measurements will be performed to confirm device performance with the following goals. (1) Kinetic study on new material epitaxy scenarios and the interplay of various photonic coupling. (2) Verify a new solution for high-quality thin film materials lift-off and hetero-integration, solving the lattice matching constraints in conventional hetero-integration methods. (3) Applying novel EO material of BTO (with among highest Pockels coefficient) for efficient EO applications.

This study will advance semiconductor technologies and promote academic research on photonics integration and nanophotonic physics.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.