Frequency-swept (chirped) infrared photothermal radiometry was combined wit
h conventional single-frequency modulation of an Ar ion laser beam to yield
a quantitative study of the surface-state annealing process induced by the
low fluence laser beam on n and p-type Si wafers. The appearance of 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 carrier minority lifetimes and diffusion coefficient were not
affected by the laser-surface interaction, but the front surface recombina
tion velocity strongly decreased with the time exposure, in the case of n-S
i (positive transient). It was found that in the case of p-Si wafers with n
egative transient both carrier-lifetime and front surface recombination vel
ocity exhibit changes. A two trap rate model was advanced to explain the po
sitive transient behavior in terms of surface-state annealing and carrier i
njection.