Dewetting During Crystal Growth of (Cd,Zn)Te:In under Microgravity

The phenomenon of "Dewetting" during crystal growth has been observed in several microgravity experiments for different semiconductor crystals. The results of these experiments showed an improvement of the material quality due to the contact-less growth of the crystals. A number of crystal growth techniques have been used to grow CZT. The most widely used is the growth from the melt by the Bridgman method. However the crucible, which is generally made of carbon-layered silica glass, causes a number of problems: solid-liquid interface curvature, spurious nucleation of grains and twins, thermal stresses during the cooling of the crystal. This work is concentrated on the growth of high resistivity (Cd,Zn)Te:In (CZT) crystals by using the phenomenon of dewetting and its application in the processing of CZT detectors. Two Cd0.9Zn0.1Te:In crystals were grown under microgravity on the Russian FOTON satellite in the Polizon facility in September 2007. One crystal was grown under a rotating magnetic field during the phase of homogenization to destroy the typical tellurium clusters in the melt. The other crystal was superheated with 20 K above the melting point. A third crystal has been grown on the ground in similar thermal conditions. Inspection of the surface of the space grown crystals gave the evidence of successful dewetting during the crystal growth. The influence of the dewetting on the material properties is shown by the results of optical and electrical characterization methods. Finally, CZT detectors have been processed from the grown part of the different crystals. The influence of dewetting on their performance will be studied by means of the detector measurements with X- and Gamma-ray sources