Ingot annealing was an indispensable process for a GaAs single crystal to improve its electric characteristics. One of the technical problems of GaAs ingot annealing was 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 was related to dislocation density, and this model was extended to a multi-axial stress state. The first code was an axisymmetrical finite element computer code, in which a bulk single crystal was assumed to be isotropic, and crystal anisotropy in elastic constants and specific slip directions was completely neglected. The second one was an axisymmetrical finite element computer code, in which the crystal anisotropy was approximately considered using averaging technique. The third one was a fully three-dimensional computer code, in which the crystal anisotropy was 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 were compared among the three computer codes.

Dislocation Density Analysis of GaAs Bulk Single Crystal during Ingot Annealing Process. N.Miyazaki, A.Kumamoto, C.Harada: Journal of Crystal Growth, 2004, 271[3-4], 358-67