Investigation of semi-insulating Cs₂Hg₆S₇and Cs₂Hg_6-xCd_xS₇ alloy for hard radiation detection

A new method is described to synthesize the semiconductor Cs₂Hg₆S₇ and its alloy with Cd. Using the assynthesized material, large single crystals have been grown by the Bridgman method under an improved set of crystal growth parameters. In addition, Cd alloying in the form of Cs₂Hg_6-xCd_xS₇ (x = 0.25, 0.5, 0.75, etc.) as well as doping with In, Cl was investigated and the influence on the electronic properties was studied. Cd alloying increases the band gap of Cs₂Hg₆S₇ from 1.63 to 1.84 eV. Doping with In and Cl however creates electron carriers and changes p-type samples of Cs₂Hg₆S₇ into n type. A 30-fold increase in the resistivity of the single crystals from 2 × 10⁶ to 0.65 × 10⁸ Ω cm has been achieved. The carrier mobility-lifetime product of the Cs₂Hg₆S₇ crystals has been increased to 1.7 × 10^-3 cm²/V for electrons (μτ)_e and 2.4 × 10^-3 cm²/V for holes (μτ)_h (HgCl₂ doped). The measured (μτ)_e value is comparable to the commercial CdZnTe crystal while the (μτ)_h is 10 times higher. Detection of Ag X-ray radiation is demonstrated using the as-grown Cs₂Hg₆S₇ crystals. (Graph Presented).