Graphene photodetectors have exhibited high bandwidth and capability of being integrated with silicon photonics (SiPh), holding promise for future optical communication devices. However, they usually suffer from a low photoresponsivity due to weak optical absorption. In this work, we have implemented SiPh-integrated twisted bilayer graphene (tBLG) detectors and reported a responsivity of 0.65 A W^–1 for telecom wavelength 1,550 nm. The high responsivity enables a 3-dB bandwidth of >65 GHz and a high data stream rate of 50 Gbit s^–1. Such high responsivity is attributed to the enhanced optical absorption, which is facilitated by van Hove singularities in the band structure of high-mobility tBLG with 4.1^o twist angle. The uniform performance of the fabricated photodetector arrays demonstrates a fascinating prospect of large-area tBLG as a material candidate for heterogeneous integration with SiPh.

Transferred graphene provides a promising III-nitride semiconductor epitaxial platform for fabricating multifunctional devices beyond the limitation of conventional substrates. Despite its tremendous fundamental and technological importance, it remains an open question on which kind of epitaxy is preferred for single-crystal III-nitrides. Popular answers to this include the remote epitaxy where the III-nitride/graphene interface is coupled by nonchemical bonds, and the quasi-van der Waals epitaxy (quasi-vdWe) where the interface is mainly coupled by covalent bonds. Here, we show the preferred one on wet-transferred graphene is quasi-vdWe. Using aluminum nitride (AlN), a strong polar III-nitride, as an example, we demonstrate that the remote interaction from the graphene/AlN template can inhibit out-of-plane lattice inversion other than in-plane lattice twist of the nuclei, resulting in a polycrystalline AlN film. In contrast, quasi-vdWe always leads to single-crystal film. By answering this long-standing controversy, this work could facilitate the development of III-nitride semiconductor devices on two-dimensional materials such as graphene.

Ferroelectrics have great potential for nonvolatile memory and next-generation electronics, but conventional ferroelectric oxide films generally suffer structural nonuniformity, interfacial depolarization, and performance degradation, particularly when downscaled to advanced technology nodes. We demonstrate uniform, wafer-scale synthesis and back-end-of-line–compatible integration of ultrathin van der Waals (vdW) high-dielectric constant ferroelectric oxide Bi ₂ SeO ₅ , retaining an optimal coercive field and robust ferroelectricity at monolayer thickness. Ultrathin vdW ferroelectric oxides formed atomically uniform interfaces with two-dimensional semiconductors and yielded ferroelectric field-effect transistor (FeFET) arrays with a low operating voltage (0.8 volts), exceptional cycling endurance (>1.5 × 10 ¹² cycles), fast write speed (20 nanoseconds), high on/off ratio (10 ⁶ ), 10-year retention, ultralow energy consumption (2.8 femtojoules per bit per square micrometer), and <5% device-to-device variation. Reconfigurable logic-in-memory circuits with these FeFETs function at supply voltages of <1 volt.