Effect of light on electrical and photoelectrical characteristics of Al/TiO₂/p-Si Schottky diode

The heterojunction Al/TiO₂/p-Si/Al has been fabricated by forming a TiO₂ thin film on p-Si wafer and Al metal was evaporated as front and back contact on the film. The XRD analysis showed the pure anatase phase with tetragonal structure. The Raman measurement also indicated that bands of TiO₂ film are characterized by the anatase phase. The transmittance and optical bandgap of thin film TiO₂ bilayer were found 74% and 3.30 eV, respectively. The current-voltage (I–V) measurements of Al/TiO₂/p-Si/Al were carried out in dark and under various illuminations ranged from 40 to 100 mW/cm² at room temperature. It was seen that the structure has a perfect rectifying property in dark. The characteristic parameters of diode such as ideality factor and barrier height were determined from I–V measurement as 1.91 and 0.71 eV. Whereas the series resistance of the device was calculated as 17.15 kΩ by using Norde's function. Moreover, the effect of light on the photoelectrical properties like V_oc and I_sc of this structure was studied and the device has a photovoltaic behavior. Furthermore, the diode has a strong response to the optical illumination so this structure can be used as photodiode or photosensor applications. The diode Al/ TiO₂ /p-Si has a perfect photosensitivity and high photoresponse properties. The transient photocurrent of the device enhances after exposing to the light with various intensities 60–100 mW/cm². The C–V and G-V measurements were performed with different applied frequencies at 300 K. The capacitance of this diode decrease with increasing frequency and the strong effect of the interface state on the total capacitance was reported.