Numerical Simulation of CdTe Crystal Growth Using the Vertical Gradient Freeze Technique Assisted by Axial Low-Frequency Oscillations of the Melt

Abstract

The problem of intensification of the melt crystal growth process has been analyzed using CdTe as an actual material. Numerical simulation of 100 mm diameter CdTe crystal growth using the VGF technique has been carried out. The heat–mass transfer was controlled by introducing low-frequency oscillating baffle into the melt, which is a so-called axial vibrational control (AVC) technique. The baffle configuration has been optimized to destroy solid “tails”, which were formed near the crucible walls at high cooling rates due to the low thermoconductivity and the corresponding latent heat. Analysis of CdTe homogeneity range showed that during fast crystal cooling, Te micro precipitations were formed, resulting from the decay of oversaturated Cd-rich nonstoichiometric solid solution during the Bridgman crystal growth technique. After full crystallization, a VGF-grown CdTe crystal stays inside the phase field of the high-temperature wurtzite polymorph. This makes it possible to go through the polymorph transition without Te micro-precipitating using the advantages of the VGF-specific feature of very slow cooling.

Axial Vibration Control Technique for Crystal Growth from the Melt: Analysis of Vibrational Flows’ Behavior

“…In conclusion, it should be noted that the AVC method is very energy efficient in terms of controlling flows in the liquid phase [22][23][24]. At the same time, the AVC method allows one to potentially overcome the scaling problem when increasing the diameter of the growth system from 20 mm to 200 mm or more without significantly changing the design of the vibration actuator.…”

“…Taking into account the crystallization heat of the substance, the melt will be set in motion. Depending on the crystal growth rate, the crystallization heat value, and the thermal conductivity of a given substance in the melt and solid, thermal convection in the absence of vibrations can be easily assessed [24].…”

Thermal Field Simulation and Optimization of PbF2 Single Crystal Growth by the Bridgman Method

“…As the crucible continues to move in a vertical downward direction, the formed S-L interface and temperature distribution changes. In the areas with large temperature gradients, the melt can be driven to solidify to the crystal and simultaneously affects the temperature field distribution by releasing heat and changing the ratio of the melt/crystal existence [9][10][11]. Therefore, the conditions of the temperature field are one of the crucial conditions that ensures the normal growth of crystals in the actual crystal growth.…”