Silicon – germanium epilayers: physical fundamentals of growing strained and fully relaxed heterostructures

Ge_xSi_1–x/Si heterostructures involving two elemental semiconductors are becoming an important element in microelectronics. Their epitaxial growth requires a detailed knowledge of the mechanisms of elastic and plastic deformations in continuous and island films both at the early stages of epitaxy and during the subsequent heat treatment. The present work is a systematic review of current ideas on the fundamental physical mechanisms governing the formation of elastically strained and plastically relaxed Ge_xSi_{1– x}/Si heterocompositions. In particular, the use of compliant and soft substrates and the epitaxial synthesis of nanometer-sized islands ('quantum dots') are discussed.