The electronic properties of hydrogen in carbon-doped n-type silicon have been studied using deep-level transient spectroscopy. It is demonstrated that hydrogen (H) in the presence of substitutional carbon (C) forms an H-C complex with an energy level located almost-equal-to 0. 16 eV below the edge of the conduction band. The H-C complex is a deep donor which is only stable in the positively charged state and dissociates after capture of free electrons for temperatures T greater-than-or-equal-to 300 K. The H-C dissociation kinetics yield an activation energy of 0.73 eV.