Gase And Gate Anisotropic Layered Semiconductors For Radiation Detectors

High quality detector grade GaSe and GaTe single crystals have been grown by a modified vertical Bridgman technique using high purity Ga (7N) and in-house zone refined (ZR) precursor materials (Se and Te). A state-of-the-art computer model, MASTRAPP, is used to model heat and mass transfer in the Bridgman growth system and to predict the stress distribution in the as-grown crystals. The model accounts for heat transfer in the multiphase system, convection in the melt, and interface dynamics. The crystals harvested from ingots of 8-10 cm length and 2.5 cm diameter, have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, low temperature photoluminescence (PL), atomic force microscopy (AFM), and optical absorption/transmission measurements. Single element devices up to 1 cm(2) in area have been fabricated from the crystals and tested as radiation detectors by measuring current-voltage (IN) characteristics and pulse height spectra using Am-241 source. The crystals have shown high promise as nuclear detectors with their high dark resistivity ( >= 10(9) Omega.cm), good charge transport properties (mu tau(e) similar to 1.4x10(-5) cm(2)/V and mu tau(h) similar to 1.5x 10(-5) cm(2)/V), and relatively good energy resolution (similar to 4% energy resolution at 60 keV). Details of numerical modeling and simulation, detector fabrication, and testing using a Am-241 energy source (60 keV) is presented in this paper.