| Cadmium zinc tellurium(Cd1-xZnxTe)crystal,for its excellent photoelectric character,has attracted more and more researchers’ attention.Cd0.96Zn0.04Te crystal,which is usually used as substrate for high-performance cadmium mercury tellurium infrared detectors,is especially noticeable.However,the problems existing in Cadmium zinc tellurium growth,such as high production cost,poor quality and small volume of the grown crystals and so on have not been solved completely.Travelling heater method(THM),as a method for manufacturing large volume and high quality crystals at low cost,is expected to solve such problems.But cadmium zinc tellurium crystal grown by THM still has the problems of low growth velocity,immature process parameters and so on.In this paper,the factors affecting of quartz ampoule coating technologies are studied,which used in Cdl-xZnxTe crystal growthing.The process parameters are optimized by orthogonal experimental.The experimental results show that the coating temperature is the most significant factor affecting the carbon film quality,followed by the coating time,and then the cooling time.While the gas flux rate affects the carbon film quality only a little.The optimized technological parameters are,the coating temperature of 1010℃,coating time of 6h,the cooling time of 18h,and the gas flux 6L/h.With the optimized parameters,the thickness of the carbon film is uniform,and its binding force with quartz is strong.In order to solve the problems mentioned above,the simulation studies of Cd0.96Zn0.04Te crystal grown by THM were carried out by Marc finite element software.The influences of various process parameters on the crystal quality,such as crucible material,crucible boundary temperature,growth rate and so on were discussed.And on this basis the process parameters were optimized.The main research contents are as follows:Simulation studies of the influences of quartz crucible and graphite crucible on zinc cadmium tellurium crystal grown by THM were carried out.By comparing the differences of the temperature gradient of tellurium solvent area and seed crystal area,the maximum temperature of tellurium solvent area,the solid-liquid interface shape,and taking into account of our actual experimental conditions,we think quartz crucible coated with a thin layer of graphite is better.The influences of different overheat temperatures on the quality of zinc cadmium tellurium crystal grown by THM with same radius were discussed.By comparing the differences of temperature gradient,heat flux,and solid-liquid interface shape,we consider an overheat temperature about 100K is ideal when grows Cd0.96Zn0.04Te single crystal with 20 mm radius by THM.The influences of different growth speed on the quality of zinc cadmium tellurium crystal grown by THM were simulated,and the qualitative relationship between the crystals grow radius and the growth speed was discussed as well.By comparing the differences of temperature,temperature gradient,heat flux,and the solid-liquid interface shape,we find out a growth speed at about 4.6×10-5mm/s is ideal when grows Cd0.96Zn0.04Te single crystal with 20 mm radius by THM.Two Φ40 Cd0.96Zn0.04Te are prepared by vertical Bridgman method with accelerated crucible rotation technical(ACRT-VB).The dislocation is shown by the etching method with Everson corrosive.The dislocation density in the crystal is statisticed with etch pith density(EPD)method.The EPD in the bottom of the crystals is much higher than that at the top area of the crystals;The EPD at the peripheral of the crystal adhered to the inner wall of the crucible is much higher than that at the top of the crystal.ACRT significantly increases the crystal dislocation density.Different parameters,the dislocation density increases in the extent also different. |
