Mono‐ and Bilayer MoS ₂ Photodetectors: High‐Performance Broadband AC Readout With Color‐Selective Noise Suppression

ABSTRACT Low‐frequency (1/ f ) noise is a primary limiter in visible photodetectors, producing baseline drift and obscuring weak signals. We engineer a broadband alternating‐current (AC) photodetection platform by integrating partially overlapped mono‐ and bilayer molybdenum disulfide (MoS 2 ), grown via chemical vapor deposition and transferred on interdigitated electrodes. The AC readout decouples modulated photocurrent from slow drifts across a wide temperature range (243–323 K). Correlative structural and optical characterization confirms heterogeneous mono‐ and bilayer MoS 2 structure with a strong ∼1.85 eV excitonic transition. Operating at 0 V bias, the device achieves ultrahigh responsivity (6.60 × 10 5 A W − 1 ), specific detectivity (2.76 × 10 15 Jones), bandwidth‐integrated specific detectivity (1.64 × 10 14 Jones), external quantum efficiency (2.04 × 10 8 %), and a response time of ∼3.1 ms at 405 nm (298 K, 100 Hz). Comparable performance persists at 532 and 635 nm and remains stable from 20 Hz to 1 kHz. Moreover, wavelength‐dependent kinetics reveal two‐step, trap‐assisted transients at 405 and 532 nm vs. a single‐step response at 635 nm, consistent with resonant excitonic absorption. Notably, noise spectra steepen from to at 532 nm, attributed to trap‐mediated mid‐gap states resulting in charge accumulation. Together, these results demonstrate a low‐noise, high‐gain, fast AC photodetector.