Role of interfacial oxide layer thickness and annealing temperature on structural and electronic properties of Al/Ta2O5/TiO2/Si metal-insulator-semiconductor structure

In this study, we investigated the structural and electrical properties of TiO2/Ta2O5 stacks prepared using DC reactive magnetron co-sputtering for as-deposited films and films annealed at 700 °C. X-ray diffraction studies revealed that the as-deposited films were amorphous, whereas those annealed at 700 °C were polycrystalline with mixed phases of TiO2 and β-phase Ta2O5. The presence of mixed phases of TiO2 and β-phase Ta2O5 was also confirmed by Fourier-transform infrared spectroscopy. The optical band gap of the TiO2 films was 3.46 eV for the as-deposited films and decreased to 3.35 eV with increasing Ta2O5 layer thickness on TiO2. The films annealed at 700 °C showed a decrease in band gap to 3.32 eV for TiO2, and this value further decreased to 3.15 eV with increasing Ta2O5 layer thickness on TiO2. Furthermore, we investigated the electrical properties of the sputtered TiO2/Ta2O5 stacks fabricated on a metal-insulator-semiconductor (MIS) Al/Ta2O5/TiO2/p-Si Schottky diode. We studied the variation of the fundamental Schottky barrier characteristics (ideality factor, Schottky barrier, and series resistance) for a diode prepared using reactive magnetron sputtering with TiO2/Ta2O5 as a thin insulating layer at the Al/p-type Si interface with different thicknesses at both room temperature and 700 °C. Improved electrical characteristics were observed for the annealed Al/Ta2O5/TiO2/p-Si MIS Schottky structure compared with those of the as-deposited structure.