Analyses Of Crystal Growth And Performance Characterization Of Detector-grade Vanadium Doped Cadmium Manganese Telluride Crystal

Cd_1-xMn_xTe（abbreviated as Cd Mn Te or CMT,cadmium manganese telluride）crystal is considered to be an ideal Hg_1-yCd_yTe epitaxial substrate and promising x-ray and gamma-ray detector materials at room temperature.However,the crystal quality is one of the main factors of the stable and efficient operation of the device.So how to prepare CMT crystals with large size and uniform composition is very important.Therefore,in this paper,the vertical Bridgman method was used to grow the detector grade CMT crystal,and the quality of the prepared CMT crystal was evaluated.The optical,electrical,thermal,and mechanical properties of the crystal were characterized respectively,and a CMT detector was fabricated subsequently.The selection of suitable growth method and process parameters is the primary condition for growing high quality CMT crystals.In this study,a modified Te solution vertical Bridgman method and Vanadium doping(5×10¹⁷ atoms/cm³)were used to successfully grow aФ30 mm Cd_0.9Mn_0.1Te:V（abbreviated as VCMT）ingot.The temperature gradient at the growth furnace interface is 10°C/cm,and the growth temperature is 1010°C,the melt is overheated at 40 K in the initial stage,the selected temperature gradient is 10～15 K·cm^-1,and the corresponding growth rate is 0.1 mm·h^-1.After the end of the growth,the temperature of the upper and lower furnaces is reduced to860°C at the same time,and the temperature is maintained for 72 hours.The powder X-ray diffraction data proved that the crystal has a single sphalerite structure.Thermogravimetric analyzer was used to analyze the thermal properties of VCMT crystals.The crystals began to lose weight within the temperature range of734.45-1049.28℃,indicating that VCMT has high thermal stability.The mechanical properties of VCMT crystals were analyzed by Vickers microindentation hardness method,and the crack surface morphology around the indentation was recorded.In addition,classical Meyer’s law,Hays–Kendall’s law and the PSR model were applied to analyse the microhardness behaviour.Important mechanical parameters of microhardness,fracture toughness and yield strength were obtained,respectively.The optical properties of VCMT crystals were studied based on infrared transmission spectrum and ultraviolet-visible-near infrared spectrum.In the mid-infrared incident light band with a wave number of 4000～500 cm^-1,the infrared transmittance of the ingot head,middle and tail remained above 57%,and the infrared transmittance of the middle wafer is close to the theoretical value.UV-VIS-NIR analysis showed that the cut-off wavelength was over 800 nm,and the crystal quality in the middle was better.The electrical properties of the VCMT crystal were studied by I-V test.The resistivity was 10⁹～10¹⁰Ω·cm,indicating that deep-donor level Te antisites pinned the Fermi level at the mid band-gap position.A VCMT detector was fabricated with planar configuration structure,which showed a resolution of11.62%of the ²⁴¹Am at 59.5 ke V peak.