Exploring the dielectric and AC transport characteristics of Au/(Sn:Fe2O3)/n-Si diodes using impedance spectroscopy over extended frequency and voltage intervals

This work focuses on the evaluation of essential dielectric characteristics of the (Sn:Fe2O3) interlayer, including the real and imaginary components of the complex dielectric constant (epsilon* = epsilon ' - j epsilon ''), electric modulus (M* = M ' + jM ''), and complex impedance (Z* = Z ' - jZ ''). To enhance the accuracy of the analysis related to dielectric response and charge transport mechanisms, capacitance and conductance were measured under varying frequencies (0.5 kHz to 2 MHz) and applied bias (+/- 3 V). The epsilon '' and tan delta versus ln(f) profiles reveal distinct peak formations within the voltage window of 0.7 V to 3 V, with their shifting positions attributed to voltage-induced rearrangements of trapped charges and polarization effects. Dielectric loss (tan delta), AC conductivity (sigma ac), and phase angle (theta) were also derived from the experimental data. The analysis confirms a strong dependence of these parameters on both frequency and voltage, particularly at low and intermediate frequencies where interface states, Maxwell-Wagner polarization, and series resistance significantly affect the response. Remarkably, the (Sn:Fe2O3) interlayer exhibits a high dielectric constant (epsilon ' approximate to 337.8 at 0.5 kHz), surpassing that of SiO2 by nearly 89 times, highlighting its potential as a high-k dielectric with enhanced energy storage capability in metal-semiconductor structures. The impedance spectra (Nyquist plots) show single semicircles, typical of Debye-type relaxation. Additionally, the ln(sigma ac) vs. ln(f) graph exhibits three distinct linear regions, each corresponding to different dominant conduction processes active at low, mid, and high frequencies.