Photothermal rate-window spectrometry for noncontact bulk lifetime measurements in semiconductors

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Abstract
A new noncontact technique for the determination of excess carrier lifetimes in semiconductors is presented. The technique employs a square laser pulse (hν≥Eg) and measures the infrared photothermal radiometric response of the sample. By applying the photothermal rate‐window concept, the excess photoexcited carrier bulk lifetime was measured with optimal signal‐to‐noise (S/N) ratio and simple, unambiguous interpretation from the maximum position of the rate‐window signal. The technique has been applied to Au‐, Fe‐, and Cr‐doped Czochralski silicon crystals. The experimental results from boxcar and lock‐in rate‐window methods were found to agree very well. The results are further mostly in agreement with those from the noncontact laser/microwave detection method.