Development of Three-Dimensional Dislocation Density Analysis Code for Annealing Process of Single Grystal Ingot.

Abstract

Ingot annealing is indispensable process for GaAs single crystal to improve its electric characteristics. One of the technical problems of GaAs ingot annealing is the increase of dislocation density during its annealing process which affects the performance of electronic devices. A computer code was developed for dislocation density evaluation of a single crystal ingot during annealing process. In this computer code, the temperatures in a single crystal ingot were used as input data, which were obtained from transient heat conduction analysis of an ingot. A dislocation kinetics model called Haasen-Sumino model was used as the constitutive equation. In this model, creep strain rate was related to the dislocation density, and this model was extended to the multiaxial stress state based on the theory of crystal plasticity. Three-dimensional finite element model was used to take account of crystal anisotropy such as elastic constants and specific slip directions. Dislocation density analyses were performed using this computer code for GaAs ingots of 4-inches diameter, and the time variations of dislocation density and stress and the residual stress after the ingot annealing were obtained by this computer code.