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

A new noncontact technique for the determination of excess carrier lif etimes in semiconductors is presented. The technique employs a square laser pulse (hv > E(g)) and measures the infrared photothermal radiome tric response of the sample. By applying the photothermal rate-window concept, the excess photoexcited carrier bulk lifetime was measured wi th optimal signal-to-noise (S/N) ratio and simple, unambiguous interpr etation from the maximum position of the rate-window signal. The techn ique has been applied to Au-, Fe-, and Cr-doped Czochralski silicon cr ystals. The experimental results from boxcar and lock-in rate-window m ethods were found to agree very well. The results are further mostly i n agreement with those from the noncontact laser/microwave detection m ethod.