CsCdInQ₃ (Q = Se, Te): New photoconductive compounds as potential materials for hard radiation detection

Two new compounds CsCdInQ₃ (Q = Se, Te) have been synthesized using a polychalcogenide flux. CsCdInQ₃ (Q = Se, Te) crystals are promising candidates for X-ray and γ-ray detection. The compounds crystallize in the monoclinic C2/c space group with a layered structure, which is related to the CsInQ₂ (Q = Se, Te) ternary compounds. The cell parameters are: a = 11.708(2) Å, b = 11.712(2) Å, c = 23.051(5) Å, β = 97.28(3) for CsCdInSe₃ and a = 12.523(3) Å, b = 12.517(3) Å, c = 24.441(5) Å, β = 97.38(3) for CsCdInTe ₃. Both the Se and Te analogues are wide-band-gap semiconductors with optical band gaps of 2.4 and 1.78 eV for CsCdInSe₃ and CsCdInTe ₃, respectively. High-purity polycrystalline raw material for crystal growth was synthesized by the vapor transfer method for CsCdInQ₃. Large single crystals up to 1 cm have been grown using the vertical Bridgman method and exhibit photoconductive response. The electrical resistivity of the crystals is highly anisotropic. The electronic structure calculation within the density functional theory (DFT) framework indicates a small effective mass for the carriers. Photoconductivity measurements on the as grown CsCdInQ₃ crystals gives high carrier mobility-lifetime (μτ) products comparable to other detector materials such as α-HgI₂, PbI₂, and Cd_xZn_1-xTe (CZT).