Dislocation density analysis of GaAs bulk single crystal during ingot annealing process (comparison among several computational methods)

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 in dislocation density during its annealing that affects the performance of electronic devices. Three computer codes were utilized for dislocation density evaluation of a single crystal ingot during its annealing. These codes employ a dislocation kinetics model called the Haasen–Alexander–Sumino model as the constitutive equation. In this model, creep strain rate is related to dislocation density, and this model is extended to a multiaxial stress state. The first code is an axisymmetric finite element computer code, in which a bulk single crystal is assumed to be isotropic, and crystal anisotropy in elastic constants and specific slip directions is completely neglected. The second one is an axisymmetric finite element computer code, in which the crystal anisotropy is approximately considered using averaging technique. The third one is a fully three-dimensional computer code, in which the crystal anisotropy is completely taken into account. Dislocation density analyses were performed for a GaAs ingot with 4-in diameter, and the time variations and distributions of the dislocation density were obtained by these computer codes. The results are compared among the three computer codes.