Simulation, modeling, and crystal growth of Cd0.9Zn0.1Te for nuclear spectrometers

• Published in: Journal of electronic materials 2006-06, Vol.35 (6), p.1251-1256
• Main Authors: MANDAL, Krishna C, SUNG HOON KANG, HOLCOMB, David E, WRIGHT, Gomez W, WILLIAMS, Joseph A, CHOI, Michael, BELLO, Job, LILI ZHENG, HUI ZHANG, GROZA, Michael, ROY, Utpal N, BURGER, Arnold, JELLISON, Gerald E
• Format: Article
• Language: English
• Subjects: CHARGE TRANSPORT; COMPUTERS; Condensed matter: electronic structure, electrical, magnetic, and optical properties; CONVECTION; Cross-disciplinary physics: materials science; rheology; CRYSTAL GROWTH; DETECTION; ELECTRONS; ELLIPSOMETRY; ENERGY RESOLUTION; Exact sciences and technology; Growth from melts; zone melting and refining; HEAT TRANSFER; INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; MASS TRANSFER; Materials science; Methods of crystal growth; physics of crystal growth; MONOCRYSTALS; Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity); Optical constants: refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of bulk materials and thin films; Physics; PRECURSOR; RADIATION DETECTORS; REFRACTIVE INDEX; ROUGHNESS; SPECTROMETERS; TRANSPORT
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-006-0250-6

High-quality, large (10 cm long and 2.5 cm diameter), nuclear spectrometer grade Cd0.9Zn0.1Te (CZT) single crystals have been grown by a controlled vertical Bridgman technique using in-house zone refined precursor materials (Cd, Zn, and Te). A state-of-the-art computer model, multizone adaptive scheme for transport and phase-change processes (MASTRAP), is used to model heat and mass transfer in the Bridgman growth system and to predict the stress distribution in the as-grown CZT crystal and optimize the thermal profile. The model accounts for heat transfer in the multiphase system, convection in the melt, and interface dynamics. The grown semi-insulating (SI) CZT crystals have demonstrated promising results for high-resolution room-temperature radiation detectors due to their high dark resistivity (rho{approximately equal to}2.8 X 10 Theta cm), good charge-transport properties [electron and hole mobility-life-time product, mutaue{approximately equal to}(2-5)X10 and mutauh{approximately equal to}(3-5)X10 respectively, and low cost of production. Spectroscopic ellipsometry and optical transmission measurements were carried out on the grown CZT crystals using two-modulator generalized ellipsometry (2-MGE). The refractive index n and extinction coefficient k were determined by mathematically eliminating the ~3-nm surface roughness layer. Nuclear detection measurements on the single-element CZT detectors with Am and Cs clearly detected 59.6 and 662 keV energies with energy resolution (FWHM) of 2.4 keV (4.0%) and 9.2 keV (1.4%), respectively.