The hydrogenation of crystalline Si by methods used to passivate defects in Si solar cells has been studied by infrared spectroscopy. For these experiments, floating-zone Si that contained Pt impurities that act as traps for H was used as a model system in which H could be directly detected. In this model system, the concentration and indiffusion depth of H were determined for different hydrogenation treatments so that their effectiveness could be compared. The postdeposition annealing of a hydrogen-rich SiN x surface layer was found to introduce H into the Si bulk with a concentration of ϳ10 15 cm −3 under the best conditions investigated here.
The nitrogen and hydrogen vibrational modes of hydrogenated GaAs(1-y)N(y) and GaP(1-y)N(y) have been studied by infrared absorption spectroscopy and density functional theory. Data for the stretching modes observed for samples containing both hydrogen and deuterium show that the dominant defect complex contains two weakly coupled N-H stretching modes. Theory predicts an H-N-H complex with C(1h) symmetry whose vibrational properties are in excellent agreement with experiment. Additional results provide further support for the defect model that has been proposed. Uniaxial stress results confirm that the symmetry of the H-N-H complex must be lower than trigonal. The vibrational properties predicted by theory for the H-N-H complex also lead to an assignment of the wagging modes that are observed. Experimental and theoretical results for GaAs(1-y)N(y) and GaP(1-y)N(y) are remarkably similar, showing that the same H-N-H defect complex is responsible for the properties of H in these fascinating materials
The postdeposition annealing of a SiNx antireflection coating is commonly used to introduce hydrogen into a multicrystalline Si solar cell to passivate defects in the Si bulk. A quantitative comparison has been made of the concentrations of H that are introduced into a Si model system from SiNx coatings with high and low density that have been characterized by infrared spectroscopy. Experiments have also been performed in which the processing of the SiNx/Si interface was modified to compare how the preparation of the interface and properties of the SiNx film itself affect the concentration of H that is introduced into the Si bulk.
Hydrogen is commonly introduced into silicon solar cells to reduce the deleterious effects of defects and to increase cell efficiency. We have developed strategies by which hydrogen in silicon can be detected by IR spectroscopy with high sensitivity. The introduction of hydrogen into Si by the post-deposition annealing of a hydrogen-rich, SiNx coating has been investigated to determine hydrogen's concentration and penetration depth. Different hydrogenation processes were studied so that their effectiveness for the passivation of bulk defects could be compared. The best conditions investigated in our experiments yielded a hydrogen concentration near 1015 cm-3 and a diffusion depth consistent with the diffusivity of H found by Van Wieringen and Warmoltz.
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