Tunable Dielectric and Charge Transport in Functionalized MWCNT/SiC Schottky Diodes for Smart Electronics

This study reports a comprehensive investigation of the electrical and dielectric properties of a Schottky barrier diode incorporating carboxyl-functionalized multiwalled carbon nanotubes (MWCNT-COOH) on an n-type 6H-SiC semiconductor substrate. The Au/MWCNT-COOH/n-6H-SiC/Au device was characterized through capacitance and conductance spectroscopy across wide range of frequency (1 kHz–1.5 MHz), temperature (300–480 K), and bias voltage (−3 to +3 V). Structural analysis confirmed a uniform spaghetti-like CNT network with high defect density, favorable for interfacial polarization and charge trapping. Electrical characterization revealed accumulation, depletion, and inversion regions, with notable features such as negative capacitance above 2 V forward bias and enhanced conductance with increasing temperature. Dielectric and electric modulus analyses demonstrated strong frequency- and temperature-dependent responses, while AC conductivity indicated multiple transport mechanisms including hopping conduction, interfacial polarization, and polaronic relaxation. The Schottky barrier height decreased from 1.51 eV at 300 K to 0.86 eV at 480 K, reflecting tunable barrier behavior under thermal stress. These results show that the MWCNT-COOH interlayer acts as an active dielectric medium, modulating charge dynamics and interfacial relaxation rather than behaving as a passive conductor. The demonstrated tunability highlights the potential of functionalized CNT/SiC heterojunctions for real-world high-temperature and frequency-adaptive devices, including gas sensors, RF/microwave rectifiers, high-speed switches, and neuromorphic elements. This work thus introduces, for the first time, a functionalized MWCNT/SiC heterojunction architecture with full dielectric characterization, paving the way for adaptive and energy-efficient next-generation smart electronics.