Growth of large-area high-quality CdZnTe substrates by the computer-controlled vertical Bridgman method

摘要

Abstract: The reproducible growth of large, high-quality CdZnTe crystals is crucial for providing low- cost substrates for IR focal plane arrays. We have grown 3-kg, 6.4-cm diameter Cd$- 1$MIN@x$/Zn$-x$/Te (x 0.04) ingots by the vertical Bridgman method, from which we have obtained large-area wafers that can yield single-crystal, twin-free substrates up to 4 cm $MUL 6 cm. The computer-controlled thermal environment was designed to reduce thermal stresses both on the solidified boule and at the melt/solid interface. The ampoule was constructed to reduce the excess Te concentration without active atmosphere control. FTIR transmission spectra of these wafers exhibited 65% transmission from 2.5 $mu@m to 20 $mu@m across the entire wafer. Glow discharge mass spectrometry (GDMS) confirmed that the concentrations of detrimental impurities were 3 $MUL 10$+14$/ cm$+$MIN@3$/. X-ray synchrotron topography showed that the substrates contained large-area subgrains with minimal residual strain at the boundaries. We discuss the suitability of these substrates for LPE growth of Hg$-1$MIN@y$/Cdx$-y$/Te (y 0.2) epilayers. !31