Model-based control of thermal stresses during LEC growth of GaAs I. Validation of thermal model

Abstract

A numerical model and a heat flux control system (HFCS) are used to control thermal stresses during LEC growth of GaAs. This model-based control strategy has resulted in growth of low dislocation density crystals. In this first part of the study, the growth configuration, design details of the HFCS, and the numerical model of the process are described, and experiments aimed at validation of the thermal aspects of the model are discussed. Results indicate good agreement between the experimental and modeling results. In the early stages of growth the difference between the predicted and measured temperature fields is found to be within the overall accuracy of model assumptions. The model accuracy in predicting the stresses in the crystal beyond the initial stages of growth is found to be ± 0.2 × CRSS of the matrix evaluated at its melting point temperature. The process model is, therefore, sufficiently accurate to provide for unambiguous and accurate control of stresses in the growing crystal at levels lower than the CRSS of the matrix.