Structural orderings of Zn_1-xCd_xTe with enhanced sensitivity to terahertz signals

The structural properties of Zn_1-xCd_xTe (ZCT) crystals were investigated by using high resolution X-ray diffraction (HRXRD) and extended X-ray absorption fine structure (EXAFS) measurements. The ZCT single crystals were fabricated with an advanced vertical Bridgeman method. Both HRXRD and EXAFS results demonstrated that the lattice constant of the ZCT crystals linearly increased with the Cd composition ratio and that the ZCT crystals for x ≈ 0.05 had a better ordered crystalline structure than the ZnTe crystals. EXAFS revealed that the atomic bond lengths had a maximum value near x = 0.05 - 0.1 and that the structural disorder in Zn_0.95Cd _0.05Te was smaller than that in ZnTe. The HRXRD and EXAFS results suggest that a small amount of Cd substituted at the Zn sites of the ZCT crystals enhanced the crystal quality. The ZCT crystals with a better crystalline structure likely have better sensing and emitting efficiencies to terahertz signals.