Progress In The Cdznte Single Crystal Growth And Substrates Fabrication

This paper presents the progress in the cadmium zinc telluride (CdZnTe) single crystal growth and high quality CdZnTe substrates fabrication at Shanghai Institute of Technical Physics (SITP). The 60 mm diameter ingots with almost 90% single-crystals were grown by the vertical Bridgman technique. The average single-crystal yield of all ingots grown in the last two years was about 60%. The large-size substrates (> 40 x 60 mm(2)) were obtained. The processing and assessment of CdZnTe substrates were introduced. Especially, the sliced wafers were etched by the bromine-methanol to remove slicing damage rather than by lapping and polishing. An Olympus BX51-IR transmission microscope with mapping function was employed to take images of the inclusions/precipitates in the full wafer and the surface of the wafers etched by the Evenson etchant. The inclusions with different shapes were investigated. The inclusions and precipitates were distinguished. The inclusions occurred at the crystal growth stage and the precipitates were separated from the nonstoichiometric crystals at the cooling stage. The both inclusions and precipitates mainly originated from the nonstoichiometric CdZnTe source materials. The mosaic structure of the etch pits profiles in the substrates has been eliminated. The etch pit density (EPD) of CdZnTe substrates was counted by the software and the average value of EPDs was less than 5 x 10(4) cm(-2). After the defects of the substrates were measured, the substrates were polished. The surface flatness and roughness of the substrates were also improved by optimizing the technology.