Ever since the invention of the transistor, a fantastic and continual growth in silicon technology has been witnessed; leading to yet more complex functions and higher densities of devices. The current book summarises the key issues of this field. Among other topics, the outlook for silicon wafer technology and silicon materials engineering in the next millennium is reviewed and new approaches to the production of a 200 GHz silicon-based devices are described. Possible applications of dislocation luminescence in silicon are discussed as well as the hopes for, and limitations of, the Si:Er - based 1.54 mm emitter. Various properties of silicon-based materials and heterojunctions are characterised by using novel and state-of-the-art measurement techniques. Hydrogen- and oxygen-related defects, rare-earth impurities as well as radiation and gettering effects are discussed from various points of view.