Material Science -- Resumé of Semiconductor Physics -- Realisation of Potential Barriers -- Electronic Device Principles -- Heterostructure Bipolar Transistors - HBTs -- Hetero Field Effect Transistors (HFETs) -- Tunneling Phenomena -- Optoelectronics -- Integration -- Outlook.Quantum size effects are becoming increasingly important in microelectronics as the dimensions of the structures shrinks laterally towards 100 nm and vertically towards 10 nm. Advanced device concepts will exploit these effects for integrated circuits with novel or improved properties. Keeping in mind the trend towards systems on chip, this book deals with silicon-based quantum devices and focuses on room temperature operation. The basic physical principles, materials, technological aspects and fundamental device operation are discussed in an interdisciplinary manner. It is shown that silicon-germanium (SiGe) heterostructure devices will play a key role in realizing silicon-based quantum electronics.