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Kinetics of Surface-State Laser Annealing in Si by Frequency-Swept Infrared Photothermal Radiometry*

Mario E. Rodríguez
Física Aplicada y Tecnología Avanzada, Universidad Nacional Autónoma de México,
Campus Juriquilla , Apdo Postal 0-1010, Querétaro, Qro,  76001, México

Frequency-swept (“chirped”) infrared photothermal radiometry was combined with conventional single-frequency-modulation of an Ar-ion laser beam to yield a quantitative study of the surface-state annealing processes induced by the low-fluence laser beam on n- and p-type Si wafers. The appearance of a signal transient was found to be strongly dependent on the electronic quality of the wafer surface and was absent in the thermally oxidized p-Si wafer. The low-injection minority-carrier lifetimes and diffusion coefficients were not affected by the laser-surface interaction, but the surface recombination velocity strongly decreased with time of exposure in samples with positive transient. A two-trap rate model was advanced to explain the transient behavior in terms of surface-state annealing and carrier ejection. In the case of samples that exhibit a negative transient we found changes in recombination lifetime as well as front surface recombination velocities but there is not changes in the carrier  diffusion coefficients.

*: Trabajo apoyado por Conacyt 32456-E-2000.

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