A numerical simulation study for the effect of applied magnetic field in growth of CdTe single crystals by the traveling heater method

Abstract

A numerical simulation study was carried out for the growth of CdTe crystals by the Travelling Heater Method to examine the effects of applied stationary and rotating magnetic fields, and also small non-uniformities in the stationary magnetic field. A strong stationary field is applied to suppress the natural convection in the solution zone, and a small but rotating magnetic field is considered for better mixing in the horizontal plane. The spatial distribution of the stationary field is almost uniform before the furnace and the growth system are lowered into the magnet opening. However, the field uniformity may be altered by the presence of the growth system. In order to determine the effect of such field non-uniformities, small magnetic body force components are considered in the model. Results show that higher stationary field levels are better in suppressing convection in the solution, but enhance the compositional non-uniformity in the solution. Small but unintentional non-uniformities in the stationary magnetic field also enhance compositional non-uniformity. A rotating magnetic field, on the other hand, is beneficial for mixing in the horizontal plane, and reduces the compositional non-uniformity in the solution. Mixing is enhanced at higher rotating magnetic field frequencies. Growth of binary and ternary alloy semiconductors such as GaSb, CdTe, CdZnTe, and InGaSb by the Travelling Heater Method (THM) is of significant technological interest. Due to high temperature gradients used in THM, strong convection in the liquid zone adversely affects the quality of grown crystals. The application of an external stationary magnetic field is an option to suppress the convective flow in the liquid zone. An external magnetic field aligned perfectly with the axis of the growth cell gives rise to a magnetic body force in the radial direction that balances the gravitational body force, and consequently suppresses the convective flow. The objective of the present article is to examine numerically the effects of the applied stationary and rotating magnetic fields on the fluid flow structures of the liquid zone in THM growth. The binary system of CdTe was selected in the numerical model. Cadmium telluride (CdTe) single crystals are being used for a variety of applications, including electro-optic modulators, prisms, Gamma ray detectors, and also as substrates for growth of ternary layers. For example, due to their good optical performance across a wide range of temperatures and adequate mechanical robustness, slices of CdTe single crystals have been used as substrates for far