It was recalled that the dislocation density could be markedly reduced by doping impurity atoms into crystals during growth. A viscoplastic constitutive equation, which coupled the microscopic dislocation density to macroscopic plastic deformation, was used as part of a crystallographic finite element model for calculating the dislocation density generated in crystals during growth. The dislocation density was considered to be an internal state variable, and the drag stress which was caused by a doped impurity was included in the constitutive equation. A GaAs crystal which was grown by using the vertical Bridgman process was used as an example for studying the influence of doping impurity and growth orientation upon dislocation generation. The results showed that doping could significantly reduce the dislocation density which was generated in the crystal. The level of reduction was also affected by the orientation during crystal growth.

Effects of Doping Impurity and Growth Orientation on Dislocation Generation in GaAs Crystals Grown from the Melt: a Qualitative Finite-Element Study. X.A.Zhu, C.T.Tsai: Journal of Applied Physics, 2000, 88[5], 2295-301