Advances and Future Challenges in Monolithic 3D Integrated Logic, Power, and Optoelectronics Technologies for Tightly Interconnected Intelligent Systems

The emergence of ultralarge-scale hardware systems for artificial intelligence is driving demand for high-performance heterogeneous integration. At the heart of these systems lies the maximization of computational capability through high data bandwidth, necessitating interconnects that either increase the number of links between tiers and chips or enhance the data transfer rate of each link. Monolithic three-dimensional (M3D) integration, particularly with two-dimensional (2D) materials, offers ultradense intertier vias and multifunctional devices within back-end-of-line-compatible processes, enabling compact vertical stacking of logic and memory. A critical challenge in this architecture is thermal management, requiring cross-layer electro-thermal analysis and codesign with integrated power regulation. In parallel, photonic integrated circuits provide low-latency, energy-efficient interchip communication by overcoming the traditional bandwidth limitation imposed by electrical signal loss, and their advantages become increasingly significant as the communication distance increases. Emerging concepts, including spectrally tunable 2D photodetectors and vertically stacked microlight-emitting-diode-photodiode transceivers, further enhance scalability by eliminating reliance on external lasers. This Review article highlights the convergence of M3D integration, 2D materials, and photonic interconnects, while outlining challenges of material compatibility, process scalability, and system-level codesign that must be addressed to realize a unified framework for next-generation computing and communication systems beyond conventional Si scaling.