Deuterium (hydrogen) incorporation in dilute nitrides (eg, GaAsN and GaPN) modifies dramatically the crystal’s electronic and structural properties and represents a prominent example of defect engineering in semiconductors. However, the microscopic origin of D-related effects is still an experimentally unresolved issue. In this paper, we used nuclear reaction analyses and/or channeling, high resolution x-ray diffraction, photoluminescence, and x-ray absorption fine structure measurements to determine how the stoichiometric [D]∕[N] ratio and the local structure of the ND complexes parallel the evolution of the GaAsN electronic and strain properties upon irradiation and controlled removal of D. The experimental results provide the following picture:(i) Upon deuteration, nitrogen-deuterium complexes form with [D]∕[N]= 3, leading to a neutralization of the N electronic effects in GaAs and to a strain reversal (from …