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A CMOS and back-side illumination-compatible single-photon avalanche diode (SPAD) is reported in 90-nm imaging technology with a peak photon detection efficiency of ≈ 44% at 690 nm and better than ≈20% at 850 nm. This represents an approximately eightfold improvement in near infrared sensitivity over existing CMOS SPADs. This result has important implications for optical communications, time-of-flight ranging, and optical tomography applications. The 6.4-μm-diameter SPAD also achieves the following: low dark count rates of ≈100 Hz with ≈51-ps FWHM timing resolution and a low after-pulsing probability of ≈0.375%.