Optical And Electrical Properties Of ZnO/PS Composite System

Abstract: The achievement of Si-based white light emission is one of the challenging goals in the field of display and lighting technologies. In this dissertation, a new way was used to realize white light emission. According to the, characteristics of the photoluminescence (PL) of porous silicon (PS) and Zinc oxide (ZnO), intensively white photoluminescence was obtained by combining the blue-green emission from ZnO films with the red emission from porous silicon layers under proper excitation wavelength.The porous silicon sample was formed by electrochemical anodization of silicon wafers. ZnO films were then deposited on porous silicon surface by pulsed laser deposition (PLD). The structure and morphologies of the samples were characterized using X-ray diffractometer (XRD) and scanning electron microscopy (SEM). The XRD pattern shows ZnO films were non-crystalline structure. Due to the roughness of the porous silicon surface, some cracks and voids appeared in the ZnO films, which could be seen from the SEM spectra. Some ZnO particles were deposited into the porous silicon pores, which made the ZnO films pinning in the substrate, increasing the adherence of the films.The influence of the substrate's preparation current density, grown temperature of ZnO films and the excitation wavelength on the photoluminescence of ZnO/PS composite was researched. It was revealed that ZnO films deposited on a larger porosity substrate and lower temperature could enhance the intensity of the samples' photoluminescence. Intensively white light emission was obtained under proper excitation.The I-V characteristics of the ZnO/PS heterostructure were different from that of the common diodes, whose reverse current was not saturated. Based on the I-V characteristics, an energy band diagram was proposed.