Frequency-dependent interface states and diode parameters of Au/n-Si Schottky diode with BOD-Z-EN interfacial layer in dark and under illumination

The Au/BOD-Z-EN/n-Si Schottky barrier diode was studied using capacitance/conductance-voltage (C/G-V) and capacitance/conductance-frequency (C/G-f) characteristics under different illumination intensities and in the dark. The increment in C and G at the low-frequency regions, at which the surface states at the semiconductor-organic interface can easily follow the applied ac signal, could be attributed to the surface states. Under illumination, the appearance of peaks in conductance versus logarithm of frequency ($G_p/\omega$- log $f$) graphs confirmed such interface trap states. It was found that the interface trap density ($D_{it}$) decreases from 5.81 × 10¹² eV⁻¹cm⁻² to 2.87 × 10¹² eV⁻¹cm⁻² while relaxation time (τ) decreases from 15.76 μs to 3.94 μs with increasing light intensity. The results showed that the barrier height (${\Phi }_B$) dropped, going from 0.667 eV (in the dark) to 0.582 eV (100 mW/cm²). The donor concentration ($N_D$) rose as the illumination intensity increased, going from 5.46 × 10¹⁵ cm⁻³ (in the dark) to 8.08 × 10¹⁵ cm⁻³ (100 mW/cm²).