Structural, electrical and red emission properties of Pd/n-ZnO/p-Si/Al heterostructures

Abstract

The ZnO thin films were grown on p-type silicon by pulsed laser deposition method for fabrication of ZnO/p-Si heterojunction. X-ray diffraction patterns were used to study the grain size and morphology of the ZnO thin film. Optical properties of ZnO thin film were studied by UV-visible, photoluminescence spectroscopy and atomic force microscopy. Experimental observations confirmed that the deposited ZnO thin films have potential for sharp emission in the visible region. High purity (99.999%) vacuum evaporated palladium and aluminium metals were used to make contacts to the n-ZnO and p-Si, respectively. The current-voltage characteristics of the Pd/n-ZnO/p-Si(100)/Al heterostructure measured over the temperature range 80 - 300 K, were studied on the basis of the thermionic emission-diffusion mechanism. The equivalent Schottky barrier height and ideality factor were determined by fitting measured current-voltage data to the thermionic emission-diffusion current equation. It was observed that the barrier height decreased and the ideality factor increased with decreasing temperature and that the activation energy plot was non-linear at low temperature. These characteristics were attributed to the Gaussian distribution of barrier heights. The capacitance-voltage characteristics of the Pd/n-ZnO/p-Si(100)/Al heterojunction diode were studied over a wide temperature range. From the measured capacitance-voltage data the impurity concentration in deposited n-type ZnO films was estimated.