Research Background
Graphene-based optoelectronic devices have attracted significant interest in silicon photonics due to their ultrahigh bandwidth and excellent compatibility with integrated platforms. However, as a single-atomic-layer material, graphene is highly sensitive to environmental factors such as interface states and dangling bonds in surrounding dielectrics, which can severely degrade device performance. This issue is particularly critical for electrically driven graphene electro-optic modulators, where interface scattering centers increase optical absorption and reduce both modulation efficiency and bandwidth. Although interface protection schemes such as hexagonal boron nitride encapsulation have been explored, preserving the intrinsic properties of large-area chemical-vapor-deposited (CVD) graphene within standard fabrication processes remains a major challenge. Therefore, developing a scalable dielectric integration strategy that enables high-quality interfaces is of great importance.
Research Content
In this work, the collaborative research team adopts a dual-layer graphene capacitor configuration with an Sb₂O₃/Al₂O₃ hybrid dielectric sandwiched between the graphene layers. The device structure of the graphene electro-absorption modulator is illustrated in Fig. 1a. By introducing an Sb₂O₃ interfacial layer, a van der Waals contact is formed, effectively suppressing interface scattering. Figure 1b presents simulations of the 3 dB bandwidth under different equivalent oxide thickness (EOT) and carrier mobility conditions, indicating that high graphene mobility plays a crucial role in enhancing bandwidth performance. The inset equivalent circuit model further reveals that both the sheet resistance of graphene and the contact resistance jointly determine the high-frequency response, providing circuit-level guidance for device optimization.
Figure 1. Device structure and bandwidth simulation schematics.
Figure 2. Dynamic Optoelectronic Performance and Data Transmission Tests
Figures 2a and 2b show the experimental setups for bandwidth and data-rate measurements, respectively. As shown in Fig. 2c, the modulator employing the Sb₂O₃/Al₂O₃ hybrid dielectric achieves a 3 dB bandwidth of up to 35 GHz, significantly outperforming devices based on a single dielectric layer (6 GHz). Figure 2d presents eye diagrams measured at data rates of 20, 25, and 30 Gbit/s, demonstrating excellent signal integrity under high-speed modulation. The energy consumption per bit is approximately 100 fJ, comparable to state-of-the-art germanium–silicon and lithium niobate modulators.
Significance and Outlook
By introducing an Sb₂O₃/Al₂O₃ hybrid dielectric structure, this study successfully establishes a high-quality van der Waals interface on CVD graphene, leading to substantial improvements in the overall performance of graphene electro-optic modulators. The proposed interface engineering strategy preserves the high carrier mobility and low carrier concentration of graphene, while experimentally achieving a 1.6-fold enhancement in modulation efficiency and a 5.8-fold increase in bandwidth, with a maximum modulation speed of 30 Gbit/s. The work also systematically investigates the impact of dielectric EOT on the efficiency–bandwidth trade-off, providing clear directions for further device optimization. This achievement not only demonstrates an ideal dielectric integration scheme for graphene optoelectronic devices but also highlights the critical role of interface control in high-performance, scalable optoelectronic integrated systems, laying a solid materials and process foundation for future high-speed, low-power photonic chips.
Professor Xingjun Wang, Professor Hailin Peng, Researcher Haowen Shu, and Researcher Jianbo Yin are the corresponding authors of this paper. Doctoral students Qinci Wu and Luwen Xing, and postdoctoral researcher Jun Qian are co-first authors. This work was supported by the Ministry of Science and Technology of China, the National Natural Science Foundation of China, and other funding agencies, with additional support from the Instrumentation Platform of the Laboratory of Molecular Materials and Nanofabrication at the College of Chemistry and Molecular Engineering, Peking University, and the State Key Laboratory of Advanced Optical Communication Systems and Networks at the School of Electronics, Peking University.
The paper, entitled “High-Speed Electro-Optic Modulator Based on Chemical-Vapor-Deposited Graphene with van der Waals Hybrid Dielectric,” was published in the international top-tier journal Advanced Materials.
Original Article Link:
https://doi.org/10.1002/adma.202517865
