PHOTOTHERMAL RATE-WINDOW SPECTROMETRY FOR NONCONTACT BULK LIFETIME MEASUREMENTS IN SEMICONDUCTORS

A new noncontact technique for the determination of excess carrier lifetimes in semiconductors is presented. The technique employs a square laser pulse (hv > E(g)) 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.