Abstract
The study reports the fabrication of undoped and Er-/Yb-doped ZnO thin films using the sol-gel spin coating technique. The structural and optical properties of the films were analyzed using X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy. Electrical characteristics were studied through current-voltage (I-V) measurements using an HP 4140B pA meter/voltage source, capable of detecting currents as low as 10(-14) A. The XRD analysis confirmed that all films exhibited a hexagonal wurtzite structure, while the PL measurements at room temperature revealed a strong ultraviolet emission with a peak wavelength at 380 nm. The I-V measurements demonstrated good rectification behavior across all temperature ranges. Schottky diodes based on Er and Yb-doped ZnO thin films showed improved rectification, a lower ideality factor, and a higher barrier height. With increasing temperature, the ideality factor decreased while the barrier height increased, indicating enhanced diode performance. It is found that the lowest ideality factor is 1.6 in Er-doped ZnO at 300 K and the highest barrier height is 0.81 eV in Yb-doped samples. It is worth noting that while the ideality factor decreased and Schottky barrier height increased with temperature indicating more ideal thermionic transport, while the rectification ratio (1.4 × 10(4)) was highest in Yb-doped samples at 50 K due to reduced reverse leakage current.