6. Defect Formation During Crystal Growth from the Melt

This chapter gives an overview of the important defect types and their origins during bulk crystal growth from the melt. The main thermodynamic and kinetic principles are considered as driving forces of defect generation and incorporation, respectively. Results of modeling and practical in situ control are presented. Strong emphasis is given to semiconductor crystal growth since it is from this class of materials that most has been first learned, the resulting knowledge then having been applied to other classes of material.

The treatment starts with zero-dimensional defect types, i.e., native and extrinsic point defects. Their generation and incorporation mechanisms are discussed. Micro- and macrosegregation phenomena – striations and the effect of constitutional supercooling – are added. The control of dopants by using the nonconservative growth principle is considered. One-dimensional structural disturbances – dislocations and their patterning – are discussed next. The role of high-temperature dislocation dynamics for collective interactions, such as cell structuring and bunching, is shown. In a further section second-phase precipitation and inclusion trapping are discussed. The importance of in situ stoichiometry control is underlined. Finally two special defect types are treated – faceting and twinning. First the interplay between facets and inhomogeneous dopant incorporation, then main factors of twinning including melt structure are outlined.