Influence of substrate bias voltage on crystallographic structure, optical and electronic properties of Al/(Ta2O5)0.85(TiO2)0.15/p-Si MIS Schottky barrier diodes fabricated by dc magnetron sputtering

Abstract

Thin films of (Ta2O5)0.85(TiO2)0.15 were prepared on p-Si and quartz substrates by reactive magnetron sputtering and the influence of substrate bias voltage (Vb) on their structural and electrical properties was studied. The crystal structure of the prepared films was elucidated by X-ray diffraction (XRD) studies. The structure of the as deposited films was found to be amorphous and the surface roughness of the films was found to be low. The crystallinity of the films was observed to be improved by increasing the substrate bias voltage. The XPS results revealed that the composition of the films were nearly stoichiometric with Vb at 0V and −150V. The optical properties of the films at various substrate bias voltages were also studied. The optical band gap of the films formed at various Vb values from 0 to −150V decreased from 4.49 to 4.39eV as revealed from the optical transmission spectra. The fabricated Al/(Ta2O5)0.85(TiO2)0.15/p-Si metal-insulator-semiconductor (MIS) Schottky diodes leakage currents at −1.5V decreased from 4.65 × 10−6A (unbiased) to 3.73 × 10−8A (Vb = −100V). On the other hand, the sample biased at Vb= −150 V exhibited an increase in leakage current (2.99 × 10−4A) when compared to all other prepared samples. Furthermore, the electrical parameters such as Schottky barrier height and ideality factor were calculated for the Al/(Ta2O5)0.85(TiO2)0.15/p-Si MIS Schottky structure and systematically investigated as a function of substrate bias voltage using current-voltage (I-V) and capacitance-voltage (C-V) characteristics.