We found experimentally a linear dependence between the 1/f noise power in the HgCdTe photodiodes and the fraction of ionized Hg vacancies in the HgCdTe layer. The number and sign of charge carriers were deduced from Hall measurements. Total point-defect concentrations were extracted by using a combination of high-resolution x-ray diffraction for precise measurements of lattice parameters and Fourier transform infrared transmission for determination the Cd content. Experimental findings support the theoretical model recently developed by Grüneis [F. Grüneis, Physica A 282, 108 (2000); 290, 512 (2001)]. © 2002 American Institute of Physics.