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ZnCdSeTe Semiconductor Compounds: Preparation and Properties Vello Valdna1, Maarja Grossberg1, Jaan Hiie1, Urve Kallavus2, Valdek Mikli2, Taavi Raadik1, Rainer Traksmaa2 and Mart Viljus2 1 Department of Materials Science, Tallinn University of Technology, 5 Ehitajate Rd., 19086 Tallinn, Estonia 2 Centre for Materials Research, Tallinn University of Technology, 5 Ehitajate Rd., 19086 Tallinn, Estonia ABSTRACT Group II-VI narrow band gap compounds CdTe, ZnCdTe and CdSeTe are known as the most suitable semiconductor materials for the room temperature gamma- and X-ray radiation detectors. In this work, we investigated electronic properties of a quaternary compound ZnCdSeTe. Cl, Cu, Pr, Er and oxygen doped host materials were synthesized from the grinded mixture of 6N purity ZnTe, CdTe and CdSe by the help of CdCl2 flux. Precautions were applied to achieve an uniform doping and high quality of the crystal surfaces. Residue phases after the thermal treatments were removed by the help of a vacuum annealing. It was found that Zn increases a substitutional solubility of dopants in ZnCdSeTe and thus, promotes optoelectronic properties of the ZnCdSeTe alloy. Cl substitutes Te whereas Cu and rare earth elements substitute Zn in ZnCdSeTe. Fabricated polycrystalline samples showed a high performance from NIR via VIS and UV to X-ray band. High stability, good linearity and performance of samples was measured under X-ray excitation of Cu KĮ 1.54056 Å, at 40 kV. INTRODUCTION Group II-VI narrow band gap compounds like CdTe, ZnTe, CdSe and its solid solutions are widely used electronic materials. CdTe is the most frequently used semiconductor material used for room temperature Ȗ- and X-ray detectors [1]. Chlorine- doped CdTe is high- or lowresistivity p-type material, depending on the chlorine concentration [2]. Clorine- and oxygendoped [3] or chlorine- copper- and oxygen-doped [4] CdTe has a high resistivity, and a negligible photoconductivity. Alloys of CdTe-CdSe containing 30 to 45 mol% CdSe could be made either cubic or hexagonal structure depending on the annealing temperature and cooling rate [5]. Chlorine-, copper- and oxygen-doped CdSe- and CdSeTe- based wurtzite structures have a high photoconductivity whereas a photoconductivity of zincblende CdTe and CdSeTe is much lower. Alloying CdTe with Zn increases the resistivity from 1E9 to 1E10-1E11 ȍcm [6, 7]. CdZnTe has emerged as one of the most attractive and promising materials for room-temperature Ȗ- and X-ray spectroscopy, for medical imaging, national security, environmental monitoring, and space astronomy [8]. Detectors based on Si or Ge material can only work efficiently at liquid-nitrogen temperature, at high X-ray photon energies, the use of Si detectors is greatly

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limited because of the reduced stopping power [9]. The energy required for generating one electron-hole pair in CdZnTe (~5 eV) is much less than that required for scintillation crystals coupled to photomultiplier tubes (~50 eV), resulting in better energy resolution [8]. The primary advantages of the re