The Effects of Doping Impurity on Dislocation Generation in InP Semiconductor Crystals

摘要

Dislocations in indium phosphide (InP) single crystals are generated by excessive stresses induced during the crystal growth process and the fabrication and packaging of microelectronic devices/circuits. The presence of dislocations has adverse effects on the performance and reliability of the InP-based devices/circuits. It is well known that dislocation density can be significantly reduced by doping impurity atoms into InP crystal during its growth, fabrication and packaging processes. A viscoplastic constitutive equation that couples a microscopic dislocation density with a macroscopic plastic deformation is employed in a transient finite element model for calculating the dislocation density generated in InP crystal during its growth, fabrication and packaging processes. The dislocation density is considered as an internal state variable and the doping impurity is represented by a drag-stress in this constitutive equation. An InP single crystal grown by the vertical gradient freeze (VGF) process is adopted as an example to study the influences of doping impurity on dislocations generated in the grown crystal. The calculated results show that doping intermediate level (～10~(17)of Ge atoms per cm~3, ～10~(18)of S atoms per cm~3) of Ge and S can significant reduce dislocation generation and produces dislocation free InP crystal except the outer edge.