The electrical properties of Au/Ti/HfO₂/n-GaAs metal/insulating layer/semiconductor (MIS) contact structures were analyzed in detail by the help of capacitance–voltage (C–V) and conductance–voltage (G–V) measurements in the temperature range of 60–320 K. The HfO₂ thin-film layer was obtained by atomic layer deposition technique (ALD). The main electrical parameters such as ideality factor (n) and barrier height (Φ_B0) were determined for Au/Ti/n-GaAs and Au/Ti/HfO₂/n-GaAs diodes using current–voltage (I–V) measurement at 300 K. The values of these parameters are 1.07 and 0.77 eV for the reference (Au/Ti/n-GaAs) diode and 1.30 and 0.94 eV for the Au/Ti/HfO₂/n-GaAs MIS diode, respectively. An interfacial charge density value of \({Q}_{ss}\)= 4.14 × 10¹² Ccm⁻² for the MIS diode was calculated from the barrier height difference of \(\Delta\Phi =0.94-0.77=0.17 \mathrm{V}\). Depending on these results, the temperature-dependent C–V and G–V plots of the device were also investigated. The series resistance (R_s), phase angle, the interface state density (D_it), the real impedance (Z′) and imaginary impedance (Z″) were evaluated using admittance measurements. The C and G values increased, whereas (Z″) and Z decreased with increasing voltage at each temperature. An intersection point being independent of temperature in the G–V curves appeared at forward-bias side (≈1.4 V); after this intersection point of the G–V plot, the G values decreased with increasing temperature at a given voltage. The intersection points in total \(Z\) versus V curves appeared at forward-bias side (≈1.7 V). The Nyquist spectra were recorded for the MIS structure showing single semicircular arcs with different diameters depending on temperature.

This work extensively investigates the operation of an Al/ Si₃N₄/p-Si Schottky-type photodiode under dark and varying illumination intensities. The photodiode is fabricated by employing the metal–organic chemical vapor deposition (MOCVD) method. A thorough electrical characterization is performed at room temperature, encompassing measurements of current–voltage (I–V), current–time (I–t), capacitance–time (C–t), and conductance time (G–t). The photodiode’s rectification factor and reverse bias area increased under illumination. The relationship between light power density, barrier height, and diode ideality factor is found. The study also found a strong correlation between light intensity and applied voltage on series resistance (R_s) and shunt resistance (R_sh). R_s values are calculated using Cheung’s functions, revealing the diode’s resistance behavior. The study also examines the photodiode’s photoconductivity and photoconductance, finding a non-linear relationship between photocurrent and illumination intensity, suggesting bimolecular recombination. Calculated photosensitivity (K), responsivity (R), and detectivity (D*) values show the device’s light response effectiveness, but efficiency decreases at higher illumination intensities. Transient experiments indicate stable and reproducible photocurrent characteristics, revealing photogenerated charge temporal evolution. This study provides a complete understanding of the Al/Si₃N₄/p-Si Schottky photodiode’s behavior under different illumination intensities. The findings advance optoelectronic device knowledge and enable their use in advanced technologies.