Horizontally aligned carbon nanotube-based rectenna for selective terahertz photodetection

Rectenna devices have emerged as a promising technology for direct detection and rectification of infrared (IR) radiation due to their rapid response and wavelength selectivity. However, practical implementation remains challenging due to antenna dimension matching with incident wavelengths, integration with suitable diodes, and resonance shifts from dielectric and substrate loading. Here, these challenges are addressed by designing and fabricating an IR rectenna based on horizontally aligned multi-walled carbon nanotubes (HA-MWCNTs) that serve as antennas for selective terahertz (THz) photodetection. An optimized metal-insulator-semiconductor (MIS) diode was fabricated and integrated with HA-MWCNTs. The CNTs were then cut into lengths between 50–750 μm corresponding to quarter-wavelength monopole antennas to obtain a rectenna structure. The optimum photo-response was observed for CNT lengths of 100 μm and 200 μm at 0.3 THz (1mm IR) and 0.15 THz (2mm IR), respectively, accounting for a shortened effective wavelength caused by the surrounding dielectric environment. Structural characteristics were investigated through SEM and AFM imaging, while spectroscopic analyses (UV–Vis, Raman, XRD, XPS) confirmed material quality, purity, and crystallinity. This approach demonstrates the potential of fabricating selective rectenna photosensors tuned by CNT length, providing key insights into wavelength-sensitive IR detection and paving the way for next-generation THz sensing technologies. • Carbon nanotube rectenna enables wavelength-selective terahertz photodetection. • CNT length precisely tuned for resonance at 0.3 THz (1 mm) and 0.15 THz (2 mm). • Focused ion beam enables controlled CNT cutting for selective antenna design. • COMSOL simulations confirm experimental resonance of CNT rectennas. • Device shows enhanced photocurrent response at resonant CNT lengths.