DEVELOPMENT OF A METHOD FOR DETERMINATION OF THERMOPELASTIC STRESSES IN GAAS PLATES

Abstract

Purpose. А study of the temperature field of the melt during the cultivation of GaAs single crystals from under a layer of liquid flux. Thermoplastic stresses were measured on plates cut from the upper, middle and lower part of the ingot of undoped GaAs.Methodology. Finite element method is used to calculate temperature profiles and internal thermoplastic stresses. The mechanism of theoretical and experimental researches which allow to predict thermoplastic stresses in the course of cultivation of ingots is offered. For the analysis and mathematical calculations of the stationary differential equation in partial derivatives and the equations of thermoelasticity, respectively, use the finite element method, the calculations were performed in the programs THERMIX and INCA. Temperature profiles and internal thermoplastic stresses were calculated. Thermoplastic stresses were measured on plates cut from the upper, middle and lower part of the ingot of undoped GaAs (cm-3) with a thickness of 1 mm with a resistivity of 108 Ohm x cm, diameter 50 mm, orientation (111).The axial temperature gradient is determined. Experimentally obtained values of ison voltage lines along the plane of GaAs plates cut from different parts of the ingot. To measure the internal (thermoplastic) stresses in the work used the method of photoelastic-guests in infrared polarized light. The integrated picture of thermoplastic stresses was obtained using the "Polaron" installation, and the point measurement with the construction of the iso-voltage line was obtained on the "Polaron-2" installation. Originality. As a result of the research it can be concluded that the mechanism of theoretical and experimental researches is offered in the work, which allows to predict thermoplastic stresses in the process of growing GaAs ingots and, finally, to develop a procedure for reducing dislocation density in GaAs ingots. The practical value. the proposed method will improve the technology of growing ingots of gallium arsenide with a more homogeneous technology, which will be a good indicator for the future creation of gas sensors from this material.