Evidence for complexes of hydrogen with deep-level defects in bulk III-V materials

Series of sharp optical-absorption lines around 2000 cm^-1 in GaAs, 2300 cm^-1 in InP, and 2200 cm^-1 in GaP are reported. They are shown to be due to the vibration of As---H or P---H bonds, the hydrogen sitting near a transition-metal impurity or other defect. The ``chemical shift'' of the line is characteristic of the impurity or defect. A model of these centers is proposed.