The Numerical Simulation On Convection And Heat Transfer During The Travelling Heater Method

Cadmium zinc tellurium single crystal is an excellent ternary compound crystal material.CdZnTe crystal,for its excellent photoelectric properties,is usually used as the nuclear radiation detector and the substrate for infiared detector epitaxial and so on.It has attracted more and more researchers' attention.At present,the cadmium zinc tellurium single crystal can be made in many preparation methods.Travelling heater method(THM),as a method for manufacturing high purity,low defect density,large volume and high quality crystals at low cost,is becoming the most promising method in the commerce.In order to obtain the process parameters of Travelling heater method for preparing cadmium zinc tellurium single crystal and shortening cycle experimental study,we use the finite element method to simulate the cadmium zinc tellurium crystal growth process with the travelling heater method.Main research contents and conclusions are as follows.The influence of different crucible radius on the heat transfer and convection in the process of cadmium zinc tellurium single crystal growth are discussed.The results showes that:with the increase of crucible radius,natural convection increases and the solid-liquid interface was still a convex one during the solidification.Crystallization of melt flow near the interface instability increases,these were not conducive to the stability of the crystal growth.The heat transfer mechanism in the cadmium zinc tellurium single crystal growth process has been studied.The results showes that:While in the process of cadmium zinc tellurium single crystal growth mainly by way of heat transfer,natural convection heat transfer could not be ignored.With the increase of acceleration of gravity,the natural convection became larger and the concavity depth increases obviously.The characteristics of natural convection and the influence of natural convection on solid liquid interface morphology in the process of cadmium zinc tellurium single crystal growth have been researched.The results showes that:the natural convection caused by the thermogravimetric effect was a counterclockwise annular flow,of which flow intensity increases at first,and then decreased as the solidification proceeds.The existence of natural convection exacerbated the solid liquid interface concavity depth.The influence of accelerated crucible rotate technique of the cadmium zinc tellurium crystal growth process with the travelling heater method on heat transfer and flow has been discussed.The results showes that:The forced convection caused by ACRT presents that a clockwise flow cell and a counterclockwise one dominate the front of the solid-liquid interface alternately,and its intensity was over that of the natural flow by 1-2 orders of magnitude.However the solid-liquid interface was still a convex one during the solidification,though the concavity depth decreases obviously.As the crucible maximum rotation rate increased,the forced convection intensity increased,the indentation depth of the solid-liquid interface decreased further.