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

Abstract

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