Cd-H pairs in GaAs: identification and stability

The Cd-H complex in Cd-111m-doped GaAs implanted with low-energy (150-400 eV) hydrogen atoms is identified and studied by perturbed angular correlation spectroscopy using radioactive Cd-111m as a probe. By measuring the fraction of Cd-H pairs in an isochronal annealing experiment, the stability of the pairs is deduced yielding a dissociation energy of E(D) = 1.35(10) eV. After Cd-111m implantation but preceding the H loading, the GaAs samples have to be annealed at temperatures exceeding 900 K in order to form Cd-H pairs. These temperatures are in agreement with the temperature range required for electrical activation of Cd implants, suggesting that a Coulombic interaction is responsible for the formation of Cd-H pairs in GaAs.