Photothermal Radiometric Frequency-Swept Studies of Kinetics Process In P-Si Wafers

Abstract

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 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 recombination velocity strongly decreased with the time exposure, in the case of n-Si (positive transient). It was found that in the case of p-Si wafers with negative transient both carrier-lifetime and front surface recombination velocity exhibit changes. A two trap rate model was advanced to explain the positive transient behavior in terms of surface-state annealing and carrier injection.