[en] The structural, electronic and charge carrier transport properties of the Zn_xHg_(1−x)Te (ZHT) ternary alloy are investigated using both ab initio pseudopotential plane wave and GW approaches within the framework of density functional theory (DFT) by the ABINIT package and virtual crystal approximation (VCA) method. Our results indicate that Hg doping inside the ZnTe semiconductor decreases the band gap and increases the charge carrier mobility of the corresponding compound meanwhile safeguarding the high electrical resistivity. In addition, Zn_0.8Hg_0.2Te satisfies conditions of a good semiconductor photo-detector at the room temperature. In the other words, the resolution and efficiency of the ZnTe as a photo-detector semiconductor improved by 20% Hg doping. (paper)