A comparative study on the electrical characteristics of Au/n-Si structures with anatase and rutile phase TiO2 interfacial insulator layer

TiO2 thin films were deposited on polycrystalline n-type Si substrate using DC magnetron sputtering system. To improve the crystal quality, thermal annealing (TA) process was done at 700 °C and 900 °C. The effect of TA on the structural properties was investigated using high resolution X-ray diffraction (HRXRD). It was observed that the phase transition from amorphous phase to anatase and rutile phases occurs at 700 °C and 900 °C, respectively. Au/TiO2/n-Si structures were also fabricated for the investigation of TA on the main electrical parameters, such as ideality factor (n), barrier height (ΦB), series resistance (Rs), shunt resistance (Rsh) and interface states (Nss). The current–voltage (I–V) and capacitance–voltage (C–V) characteristics have been investigated at room temperature and results have been compared with each other. The electrical characteristics showed that TA strongly affects the main electrical parameters. The rectifying ratio of Au/n-Si structures with anatase phase TiO2 was to be 140 while the rutile phase was to be 8864. The leakage current was also found to be very sensitive to the annealing temperature, and also the magnitude of the leakage current for rutile phase is 15 times lower than the anatase phase's. In addition, the energy distribution profile of Nss of the structures was obtained from the forward bias I–V data by taking the bias dependence of the effective barrier height (Φe) into account. For both of the samples, the value of Nss decreases with TA. Similarly, the values of Rs and Rsh of the structures obtained from the forward bias I–V data were found as 209 Ω and 42 kΩ for the anatase and 59 Ω and 598 kΩ for the rutile phase. These results show that the performance of the Au/TiO2/n-Si structure improved with thermal annealing.