Monolithic Integration of Carbon Nanotube-Based Complementary Field-Effect Transistors with 3D-Stacked Photodiodes for Unified Sensing and Computing.

Abstract

Carbon nanotubes (CNTs), combining excellent electrical and optoelectronic properties with low-temperature processability, provide a compelling materials platform for monolithic three-dimensional (M3D) integration that unifies digital logic in complementary field-effect transistor (CFET) architecture and functional sensing elements with three-dimensionally structured nondigital functional blocks. However, such a fully integrated system has not yet been experimentally demonstrated. Here, we report CNT-based digital circuits implemented in a true CFET architecture, in which vertically stacked P- and N-FETs share an identical footprint and exhibit well-balanced performance through structural engineering. A full suite of logic functions, including inverters, NOR, OR, NAND, AND gates, as well as a 4-transistor static random-access memory cell and a five-stage ring oscillator are successfully demonstrated. The CFET inverters exhibit rail-to-rail operation with large noise margins and a peak voltage gain of 147 at a supply voltage of 1 V, while maintaining a gain of 9.7 with only 3.3 pW static power consumption at 0.2 V. In parallel, CNT photodiodes are vertically stacked and cascaded to form a 3D optical sensor that delivers nearly twice the photovoltage of planar counterparts. By monolithically integrating the 3D CNT photodiode with a CNT-based CFET inverter, we further demonstrated a prototype "sensing-and-computing" module in which optical power and spectral information are directly sensed and processed within a single monolithic CNT-based block. This work establishes CNTs as a unified platform for high-density, low-power M3D integration toward near-/in-sensor and edge-computing applications.