EN
The paper summarizes a few basic properties of SiGe showing that SiGe is an interesting material for high speed electronics. The advantage of using heterostructures in silicon-based technologies is demonstrated by taking SiGe heterobipolar transistors as an example. First results obtained with very fast and low-noise heterobipolar transistors are briefly mentioned. The paper is concluded by a short discussion of a few optoelectronic properties observed in various Si/Ge and Si/Si_{1-x}Ge_{x} strained-layer superlattices and quantum wells with particular emphasis on electroluminescence properties.