Numerical Simulation Of Cd_1-xMn_xTe Crystal Growth By Vertical Bridgman Method And Cd_0.9Mn_0.1Te Crystal Co-doped With In/V

Tellurium manganese-cadmium（CdMnTe）crystal is a semiconductor material with Good photoelectric and three magneto-optical properties,which has important applications in the field of detectors for room-temperature radiation,infrared lasers,magneto-optical isolators,and also has good application prospects in the fields of security inspection,space science and nuclear technology.Therefore,the preparation of large-size,high-quality CdMnTe crystals with uniform composition has been attracting widespread attention.At present,the most commonly used preparation method for CdMnTe crystals is the Vertical Bridgman Method（VBM）,but the crystals grown by this method still have quality problems such as small single crystal size,low single crystal rate and high Te precipitation/inclusion density.In this paper,for the growth process of CdMnTe crystals,FLUENT software is used to perform global numerical simulation of VBM-grown CdMnTe crystals,and the relationship between the temperature gradient during crystal growth and the heat transfer and flow of the internal melt of the crucible and the temperature field inside the system is studied.The effects of crystal interface morphology and crystal component segregation on crystal quality were mainly explored.On this basis,the crystal growth process parameters were optimized,and the structure and photoelectric properties of the grown CdMnTe crystals were characterized by the defect concentration of the co-doping adjustment point of In and V.Firstly,a two-dimensional finite volume numerical model is established based on finite element software to simulate melt convection and interface morphology under three temperature gradients of 5K/cm,10 K/cm and 15 K/cm during VBM growth of CdMnTe crystals.The results show that with the increase of temperature gradient,the flow rate of melt in the crucible decreases,the convection intensity weakens,the flow cell splits,and the solid-liquid interface gradually flattens,which is conducive to the growth of good crystals.When the temperature gradient was 10 K/cm and 15 K/cm,the decline trend of melt content was stable in the later stage of crystal growth,the flow rate also tended to be stable,and the crystal growth rate and crucible decline rate were basically the same.The temperature change at the junction of the crucible and the melt is more moderate with the increase of the temperature gradient,the influence of natural convection on heat transfer is weakened,and the radial isotherm in the upper part of the melt becomes straighter.On the basis of numerical simulation,the temperature amplitude of change is（10～15）K/cm,the crystal growth speed is 0.15 mm/h,the superheating temperature is 30°C,and the subcooling temperature is 10°C.In/V:Cd_0.9Mn_0.1Te crystals with dimensions of（?）30 mm×100 mm were grown by overdoped with Te in and V at an in-place temperature of 1090°C,a furnace temperature of 840°C and an in-situ annealing temperature of 830°C.X-ray diffraction tests showed that the diffraction peak of In/V:Cd_0.9Mn_0.1Te crystal was completely consistent with the standard pattern,and the crystal grew along the（111）crystal plane with a single sphalerite structure.The morphology of Te inclusions/precipitation phases of the wafers at the head,middle and tail positions of the ingot was observed by infrared transmission microscopy,and it was found that the middle Te inclusion was the least and the crystal quality was better.The infrared transmittance of the crystal was analyzed by Fourier transform infrared spectrometer,and in the range of wavenumber（400～4000）cm^-1,the infrared transmittance in the middle of the crystal ingot reached 68%,and the infrared transmittance of the head and tail also reached more than 65%.UV-visible-NIR transmission spectroscopy showed that the transmission curve variation law of different samples was basically the same.In/V:Cd_0.9Mn_0.1Te crystal absorption edge wavelength is around 790 nm,when the wavelength is greater than 900 nm,the transmittance is（45～60）%,the transmittance curve tends to be straight,and the In/V:Cd_0.9Mn_0.1Te crystal band gap is about 1.59 e V.The I-V test was used to study the electrical properties of the crystal,and the results showed that the bulk resistivity of the growth state In/V:Cd_0.9Mn_0.1Te crystal reached more than 10¹⁰Ω·cm^-1,and the bulk resistivity of the middle crystal reached9.0×10¹⁰Ω·cm^-1,indicating that the crystal impurity defects in the middle of the ingot were few and the crystallization quality was good.