Hydrogen passivation of germanium dangling bond defects observed as paramagnetic GePb1 centers at the GexSi1-x/SiO2 interfaces is studied as a function of Ge concentration and thickness of the GexSi1-x layer. By correlating the results obtained by three independent defect-sensitive methods - electron spin resonance spectroscopy, ac conductance of the GexSi1-x layer, and the positron annihilation spectroscopy-with the results of strain measurements by high-resolution X-ray diffractometry, we found that the density of the Ge dangling bonds reflects residual strain in the GexSi1-x layer. Furthermore, in the layers with high strain the hydrogen passivation efficiency of dangling bonds is found to decrease, suggesting a considerable spread in the activation energies of the passivation/depassivation reactions. (C) 2013 Elsevier B. V. All rights reserved.