Optical And Electrical Properties Of Zno Composite System Based On Si-npa

Porous silicon is characterized by its simple preparation technology, high luminescence efficiency, and compatibility of post processing to silicon planar process. It is believed that porous silicon is the best silicon luminescent material and has the potential application in silicon-based photoelectrical devices and full silicon opto-electronic integrated circuit (OEIC). Based on the fully investigation to the developing history of porous silicon, we found it is still not clear and full of contradiction to some key physical properties, including the distribution of nanocrystallites in silicon skeleton, the influence of quantum confinement on the photoluminescence performance, and the carrier transport process. It is necessary of clarifying these problems to perfect the stability and performance of photoelectrical devices based on porous silicon, like electric-luminescence diode, photoelectrical detection device, etc.In the paper, we have growed different zinc oxide film on silicon nanoporous pillar array (Si-NPA) via chemical vapor deposition (CVD) method, and discussed the luminescent properties, carrier transport process of ZnO/Si-NPA Schottky junction structure, and the influence of surface pillar array of Si-NPA on the growth of ZnO film, after comparing the microstructure, optical and electrical performance with the substrate of Si-NPA.1. Microstructure and carrier transport mechanism of Si-NPASi-NPA prepared via hydrothermal etching technique possesses a triple hierarchical structure, i.e., the regular array of micron-sized silicon pillars, the high-density nanopores distributed all over the pillars, and the silicon nanocrystallites composing the pore walls. High density of silicon nanocrystallites which showed zero-dimensioned quantum dot structure was found in TEM images. Employing the chemical active behavior and template function of nanopore in Si-NPA, a composite structure system of gold nanowire and particle has been synthesized at temperature as low as 400℃. The current-voltage relationship of Ag/Si-NPA/Si diode at different measuring temperature showed that carrier transport process is mainly dominated by two mechanisms, quantum tunneling current at low voltage and thermal electron current at high voltage.2. Optical properties of core-shell structure of ZnO/Si-NPARegularly arrayed nanocomposite system of zinc oxide/silicon nanoporous pillar array (ZnO/Si-NPA) was prepared by chemical vapor deposition utilizing Si-NPA as substrate. Our experimental results disclosed that all the pillars of ZnO/Si-NPA were of a core-shell structure. Different from the red and blue emission from Si-NPA, two strong and wide emission bands were observed at ultraviolet and blue-green ranges. These emission bands were attributed to the band-edge exciton transition of ZnO crystallites and two kinds of deep-level transitions originated from its intrinsic defects.3. Structure and electrical performance of ZnO thick filmPolycrystalline thick film of zinc oxide (ZnO) was grown on a unique silicon substrate with hierarchical structure, silicon nanoporous pillar array (Si-NPA), by vapor phase transport method. It was found that as-grown ZnO film was composed of closely packed ZnO crystallites sized averagely～10μm. The film resistivity of ZnO/Si-NPA was determined to be～8.9Ω.cm by standard four probe method. The lengthwise I-V curve of ZnO/Si-NPA heterostructure was measured. Theoretical analysis shows that the carrier transport across ZnO/Si-NPA heterojunction is dominated by two mechanisms, a thermionic process at high voltage and a quantum tunneling process at low voltage.