This paper provides an overview of the technology for growing bulk silicon-germanium solid solutions and of the structural properties of the solidified materials.

It is an attempt to summarize and value the methods and efforts applied to the controlled crystallization of silicon germanium melts which were employed during the last four decades.

The especially high degree of segregation makes the system sensitive to small changes of growth conditions, which leads to inhomogeneities and strain. The future availability of homogeneous, low-defect Si-Ge crystals through the whole composition range is briefly discussed

The Si1Ge1 solid solution has experienced a great resurgence since the discovery that strained Si-Ge/Si heterostructures offer the possibility to tailor the band structure of the alloy [1, 2]. This has reactivated great interest in investigations on the Si-Ge semiconductor system. However, thin strained layers are not a suitable system for the study of bulk fundamental properties relevant to device processing. There is a need ‘.0 have bulk single crystals of this material available SixGe!^x crystals in a satisfactory quality over the whole composition range.

During the last four decades, bulk Si-Ge has been investigated mainly from a technological point of view. Emphasis was primarily put on performance problems of Si-Ge applications, e.g. in the field of photodetectors and thermogenerators (see Appendix). Therefore the studies on solidification behaviour, macro- and microsegregation effects were mostly superficial and what has been called a homogeneous crystal was more or less sufficiently homogeneous material for a certain application. Today, the possible applications of bulk Si-Ge crystals as substrates for layer structures pose higher requirements on homogeneity and crystallinity. This makes it necessary to go deeper into the technological and physical problems of Si-Ge solid solution solidification and to examine more carefully the questions on quality influencing effects, such as supercooling and phase stability.

As a first step towards the availability of low-defect single crystalline SixGe! _x, this overview tries to summarize and evaluate the already applied methods and the derived results on Si-Ge solidification and aims to point out key open questions for further research.

Tlu Si.(ici_x solid solution has experienced a great resurgence since the discovery that strained Si-Ge/Si heterostructures offer the possibility to tailor the band structure of the alloy [1, 2]. This has reactivated great interest in investigations on the Si-Ge semiconductor system. However, thin strained layers are not a suitable system for the study of bulk fundamental properties relevant to device processing. There is a need ‘.0 have bulk single crystals of this material available SixGe!^x crystals in a satisfactory quality over the whole composition range.
During the last four decades, bulk Si-Ge has been investigated mainly from a technological point of view. Emphasis was primarily put on performance problems of Si-Ge applications, e.g. in the field of photodetectors and thermogenerators (see Appendix). Therefore the studies on solidification behaviour, macro- and microsegregation effects were mostly superficial and what has been called a homogeneous crystal was more or less sufficiently homogeneous material for a certain application. Today, the possible applications of bulk Si-Ge crystals as substrates for layer structures pose higher requirements on homogeneity and crystallinity. This makes it necessary to go deeper into the technological and physical problems of Si-Ge solid solution solidification and to examine more carefully the questions on quality influencing effects, such as supercooling and phase stability.
As a first step towards the availability of low-defect single crystalline SixGe! _x, this overview tries to summarize and evaluate the already applied methods and the derived results on Si-Ge solidification and aims to point out key open questions for further research.