H MULTITRAPPING MECHANISMS AND H-2-MOLECULE FORMATION IN DOPED CRYSTALLINE SILICON

A model is proposed to explain hydrogen multitrapping and H-2 molecule formation in phosphorus- and boron-doped silicon. Two major features characterize this model: the first one concerns the existence of a metastable configuration of the hydrogen-donor complex having a donor character; the second one concerns the capability of donor atoms to trap several H ions by Coulombic attraction. These features lead to microscopic mechanisms for H trapping in Si:P more efficient than those proposed for Si:B, thus accounting for the different atomic H profiles and H diffusivities observed in the two materials. These microscopic mechanisms also provide useful suggestions for the improvement of phenomenological models of H diffusion. The existence of a metastable complex configuration having a donor character nicely agrees with the results of annealing experiments on hydrogenated Schottky diodes fabricated from Si:P.