Impact of voltage and frequency on electrical characteristics of MIS capacitors with triphenylamine layer

This study examines the effect of triphenylamine (TPA) interlayers on the electrical properties of Al/TPA/p-Si metal-interlayer/insulator material-semiconductor (MIS) capacitors. Using Gaussian software, TPA molecular structure was optimized, and HOMO-LUMO energy levels were simulated. Capacitance-conductance-voltage (C-G-V) measurements were performed at room temperature over −4 V to +4 V and 50 kHz–700 kHz. AFM and SEM analysis showed TPA films were smooth with a uniform thickness of about 178 nm. The C-V characteristics revealed a frequency-dependent decrease in capacitance, indicating a continuous distribution of interface states. Barrier height (Φ_B) increased from 0.305 eV at 50 kHz to 0.655 eV at 700 kHz, while the active interface trap density (D_it) decreased from 6.73 × 10¹² eV⁻¹ cm⁻² to 3.23 × 10¹¹ eV⁻¹ cm⁻². Additionally, the accumulating region exhibited low series resistance values (between 6.88 and 8.44 Ω). These results suggest that TPA thin films are effective for MIS capacitors.