dc.description.abstract | Recently, the applications of relaxed SiGe layers in the silicon-based electronics and photonic devices attract many attentions. The high carrier mobility of silicon channel through the adjustable lattice constant, designed energy band and defect engineering can be utilized as the start material for high-speed electronics and photonic devices. The conventional relaxed SiGe buffer layer has thick layer and rough surface. Such a structure resulted in the device with thick thickness and high cost, which suffer deterioration later lithography process and heat-up problem. In this thesis a new buffer with highly relaxed and thin relaxed SiGe layer is proposed. In this thesis, we studied thin relaxed Si1-xGex films by hydrogen ion implantation. A Si0.8Ge0.2 film grown on the substrate consisting of Si:B/Si substrate. H+ ions implant atom with dose of 2×1016 cm-2 was used as the ion source. After RTA treatment, the relaxation (78%) of Si0.8Ge0.2 on Si:B/Si is higher than that without buried boron layer and without ion implantation. By the research in this thesis, thin and relaxed SiGe can be achieved and serves as the potential candidate of starting materials for the strain-Si devices, III-V photonic devices, and solar cells.
In addition, silicon nanostructures have attracted much attention because of their unusual quantum properties and potential applications. One-dimensional semiconductor nanowires have excited much interest recently owing to their importance in fundamental research and potential applications in nanotechnologies. The exhibited unique structural, optical and electronic properties have made them the most promising material systems in areas as diverse as single electron devices, optoelectronics, sensors, and cold cathodes for field-emission displays. With different energy band structure of Germanium, SiGe nanowires and other heterostructures are highly desirable for future nano-electronics and nano-photonics applications. Various methods have been developed to prepare one-dimensional silicon nanostructures, like vapor-liquid-solid (VLS) growth mechanism. However, the growth mechanisms have some limitations as they generally need a high temperature or a high vacuum, templates and complex equipment, or they employ hazardous silicon precursors. Metal catalytic etching has been successfully developed as a method to fabricate silicon nanowires with uniform orientation. In this work, we report the formation of Si0.8Ge0.2 nanowires on Si substrates using Au assisted top-down chemical etching with polystyrene nanosphere lithography (PS NSL). And by the oxidation for SiGe, the composition of germanium in SiGe nanowires is condensed to form the high germanium consistence nanowires.
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