Investigation of changes in current-voltage and capacitance-voltage characteristics of Au/n-si schottky diodes irradiated with thermal neutrons

Au/n-Si/Ag Schottky diodes were subjected to thermal neutron irradiation to investigate the effects of thermal neutron transmutation and displacement damage. Schottky diodes were fabricated by thermally evaporating gold (Au) onto n-type Si wafers that had undergone a wet chemical cleaning process. The effects of irradiation on the Schottky barrier height (Φb), ideality factor (n), leakage current (I₀), series resistance (Rs), donor concentration (Nd), and diffusion potential (Vd) were determined using the current-voltage (I-V), capacitance-voltage (C-V) characteristics and Cheung's method. From the I-V measurements taken at room temperature before irradiation, the best ideality factor was found to be 1.24, and the zero-bias barrier height was determined to be 0.82 eV. The Schottky diodes were irradiated with thermal neutrons at two different doses: 10 seconds and 30 seconds. The initial 10-second irradiation caused minor changes in the diode parameters. After the second 30-second irradiation, significant changes in the diode parameters were observed. After the total dose, an increase in the saturation current and barrier height inhomogeneity, as well as a decrease in carrier concentration, were observed. These changes were attributed to the carrier removal effect caused by thermal neutrons. An increase in the ideality factor was observed after irradiation, while very little change was recorded in the zero-bias Schottky barrier height values. For all diodes, the zero-bias barrier height was also calculated from the reverse bias current characteristics. After the second dose, these values were found to have decreased in all diodes. Similarly, leakage current was also calculated from reverse bias current characteristics. A slight increase in leakage current was noted after the first dose, and a significant increase was observed after the second dose. The series resistance values were calculated before and after irradiation using Cheung's functions. Prior to irradiation, these values ranged from 2.10 kΩ to 2.76 kΩ, while after the second dose, the series resistance values for all diodes decreased and were found to be in the range of 1.59 kΩ to 2.20 kΩ. Additionally, the transmutation of elements in the devices due to thermal neutrons was confirmed using energy-dispersive spectroscopy (EDS) mapping. When the C-V characteristics were examined, the capacitance values in both the forward and reverse bias regions clearly decreased after irradiation. This situation was attributed to the reduction in carrier concentration caused by the irradiation.