The indium-doped CdZnTe crystal was characterized by PL spectra at 10 K and IR transmission spectra, as well as its current-voltage behavior at room temperature. The results showed that indium atoms substituted for the Cd vacancy and produced ionized donors [In-Cd](+), i.e. indium doping element recombined with [V-cd](2-) and formed the singly negative defect complex A-center [In-Cd(+)center dot V-Cd(2-)](-) and the neutral ones [2In(Cd)(+)center dot V-Cd(2-)](0) and [In-Cd(+)center dot(In-Cd(+)center dot V-Cd(2-))(-)](0). Indium doping also increased the IR absorption of the CdZnTe crystal due to the lattice absorption and free-carrier absorption. Meanwhile, indium doping increased the electrical resistivity and decreased the leakage current of CdZnTe crystals remarkably. (c) 2006 Elsevier B.V. All rights reserved.