Fabrication and characterization of nanostructure thin film ZnO Schottky contacts based UV photodetectors

Abstract

We report on characterization of Pd/ZnO nanostructure thin film Schottky contacts based UV photodetector. The ZnO film was grown on p-type Si ‹100› substrate by using vacuum thermal evaporation method. With applied voltage in the range from -2V to 2V we estimated the photocurrent, contrast-ratio, responsivity and quantum-efficiency of the photodetectors for an incident optical power of 0.1mW at 365nm ultraviolet wavelength. The I-V characteristics were studied and the parameters such as idealityfactor, leakage-current, and barrier-height of the Schottky contacts were extracted from the measured data. The surface morphological and the structural properties of the thin film were studied by atomic force microscope (AFM) and scanning electron microscopy (SEM). The bandgap of ZnO is evaluated from the absorbance spectra of ZnO thin film obtained by using double beam spectrophotometer. For the investigation of the surface chemical bonding, X-ray photoelectron spectroscopy (XPS) measurements were also performed. The device exhibited good stability, high efficiency and high sensitivity under the reverse bias condition. For forward bias, the UV detection sensitivity decreased proportionally to the bias voltage.