Dislocations in GaAs and InP crystals were generated by thermal stresses induced during their solidification process of crystal growth. High dislocation density in these crystals will reduce the performance and reliability of the GaAs- and InP-based microelectronic and photonic devices/circuits. It was known that doping impurity atoms into GaAs and InP crystals during their solidification process could significantly reduce dislocation densities generated in these crystals. A viscoplastic constitutive equation that couples a microscopic dislocation density and impurity atoms with a macroscopic plastic deformation was employed in a transient finite element model for predicting the dislocation density generated in the undoped and doped GaAs and InP crystals grown by the vertical gradient freeze process. The effects of crystal growth parameters (i.e., imposed temperature gradient, crystal diameter, and crystal growth rate) on dislocation generation were also investigated. The numerical results showed that doping impurity could significantly reduce the dislocation density generated in these crystals. It also showed that dislocation density reduces drastically as the crystal diameter and imposed temperature gradient decrease, but the crystal growth rate has almost no effect on dislocation generation in these crystals.

Finite Element Modeling of Dislocation Reduction in GaAs and InP Single Crystals Grown from the VGF Process. X.A.Zhu, G.Sheu, C.T.Tsai: Finite Elements in Analysis and Design, 2006, 43[1], 81-92