Growth And Characterization Of Large-size Cd_1-xZn_xTe Single Crystal Using Seeded Vertical Bridgman Method

Cd_1-xZn_xTe (CZT) single crystal is proved to be the most promising material for room temperature X-ray and gamma-ray detectors, and the suitable substrate for epitaxial growth of infrared detector material HgCdTe. Therefore, numerous researchers are now concentrating on the preparation of large-size CZT single crystal. In this work, CZT crystals were grown by seeded vertical Bridgman (VB) method and characterized by various methods.First, the <211> and <111> orientation seeds with the growth direction on B face are chosen based on theoretical analysis on the seeded growth principles. A Cdo.9Zno.1Te ingot named CZT1 with the dimension of Φ60×140 mm² was grown, using the techniques including the addition of excess Cd over the stoichiometric ones and a homogenization process for the seed. The crystal was also doped with indium, and a single crystal with the volumes of 200cm³ was obtained. A second CZT crystal with the concentration of Cd_0.96Zn_0.04Te named CZT2 with the same dimension of Φ60×100 mm was grown, with a higher melting point crystal seed of Cdo.9Zno.1Te, so that the melt can be superheated without melting of the seed. A single crystal with the volume over 100cm³ was also obtained in the crystal ingot.The rocking curves of double crystal X-ray diffraction are measured for the wafers cut at different parts of the ingots. Variance of the full width at half maximum (FWHM) for the curves is calculated. To evaluate Zn distribution in the as-grown ingot, the near infrared (NIR) spectra was measured, Zn distribution in the ingot was determined, from which the partition coefficient of Zn during the growth was calculated to be about 1.3. The homogeneous distribution of Zn along the radial direction indicates a flat liquid-solid interface during the crystal growth.The infrared (IR) transmission spectra of the wafers from the top, mid and tail of the ingot CZT1 were first measured. The forms of the curves are similar to each other with coincident high transmittance in the region of 2000-4000cm^-1 , while they are sharply decreased to zero from 2000cm^-1 to 500cm^-1 due to shallow level complex generated by the doped In. However, the IR transmittance is high for all the wafers from...