Preparation and Characterization of Nanostructured Silicon for Optoelectronic Applications
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Preparation and Characterization of Nanostructured Silicon for Optoelectronic Applications Y. S. Ryu1, A. Filios2, Y. Paek3 and S. Ryu3 1 Mechanical Engineering, Farmingdale, SUNY, Farmingdale, NY 11735, U.S.A. 2 Electrical Engineering, Farmingdale, SUNY, Farmingdale, NY 11735, U.S.A. 3 Materials Science & Engineering, Andong National University, Andong, Kyungbuk, Korea. ABSTRACT Silicon is by far the most successful material in the microelectronics industry enjoying a well-established fabrication and processing infrastructure. Two of the main challenges in traditional silicon electronic devices are (a) silicon’s relatively small and indirect fundamental energy band-gap, which severely limits optoelectronic applications, and (b) the absence of a suitable material to form a heterojunction barrier on silicon. Silicon based nanostructures are being explored as potential candidates to extent the applications of silicon in optoelectronics, provide for high-speed silicon quantum devices, increase the efficiency and reduce the cost in silicon photovoltaic solar cells, and facilitate cost-effective silicon sensors for biological, environmental, and other applications. Quantum size silicon nanolayers, nanowires, and nanodots embedded in oxide, nitride, and other amorphous matrices may provide an effective barrier for silicon, as well as band-gap engineering and enhanced optical transitions for solar cell and optoelectronic applications. INTRODUCTION The emerging field of nanoscale engineering holds the promise for the development of a novel generation of devices with unique characteristics. By manipulating matter at the most fundamental level, it becomes possible to tailor properties of the material such as the fundamental bandgap energy, the absorption and emission characteristics, the dielectric function, binding energy, and the density of states, so that devices can be designed to fit the specific application. In addition, self-assembled nanoscale films and nanocrystals of materials with different characteristics can be combined in a host matrix to provide heterojunctions and barrier structures which are essential components in designing devices. To date, significant progress has been made in the understanding of such nanostructures, however there are still issues that need to be resolved, such as fabrication of reliable electrical contacts to provide input and output, reducing the interface defects, surface passivation, uniformity of the nanostructured active layers and reliable interconnection between these layers, and of course cost effective methods of fabrication. Over the past 15 years, such nano-engineered structures based on silicon, the dominant material in microelectronics, have generated significant interest for their potential use in optoelectronics, high-speed electronics, and photovoltaics. Since the discovery of strong photoluminescence in the visible region of the spectrum at room temperature [1], and a blue shift in the absorption edge due to an increase in bandgap energy [2] in porous silicon, silicon-ba
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