Development of dislocation density analysis code for annealing process of single-crystal ingot

Abstract

Ingot annealing is an indispensable process for a 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, temperatures in a single-crystal ingot are used as input data, which were obtained from a transient heat conduction analysis of an ingot. A dislocation kinetics model called the Haasen–Sumino model was used as the constitutive equation. In this model, creep strain rate is related to the dislocation density, and this model which extended to the multiaxial stress state was incorporated into a finite element elastic creep analysis code for axisymmetric bodies. Dislocation density analyses were performed using this computer code for GaAs ingots of 4- or 6-in diameter, and time variations of the dislocation density and equivalent shear stress and residual stress after the ingot annealing were obtained by this computer code.