Impact of annealing treatment on structural and dc electrical properties of spin coated tungsten trioxide thin films for Si/WO3/Ag junction diode

We report on the effect of the thermal annealing on structural and electrical properties of p-Si/n-WO3/Ag junction diode. According to the XRD pattern, the WO3 films exposed that the crystalline phase transformation of monoclinic to orthorhombic structure for an increasing annealing temperature. The SEM images show an abrupt change in the plate like grain growth and surface morphology. From the UV-visible analysis, the band gap energy decreases for the higher annealing temperature. The dc electrical characterization shows that the conductivity (σdc), activation energy (Ea) and pre-exponential factor (σ0) values vary function of temperature. The Si/WO3/Ag contact junction diode parameters of ideality factor (n), barrier height (ΦB), leakage current density (J0) and series resistance (Rs) were examined by the J-V method, Cheung's and Norde functions as a function of annealing temperature according to the thermionic emission method (TE). The values of n and ΦB decrease with increasing annealing temperature and better the device performance on an optimized annealing temperature at 873 K. The temperature dependent of experimental n and ΦB revealed the presence of inhomogeneity at WO3-Ag interface. This behavior is modeled by assuming the existence of Gaussian distribution (GD) of barrier heights in temperature range 303-423 K.