  We characterize a new commercial, back-illuminated reach-through silicon
single-photon avalanche photo diode (SPAD) SAP500 (Laser Components. Inc.),
operated in Geiger-mode for purpose of photon counting. We show that for this
sensor a significant interplay exists between dark counts, detection
efficiency, afterpulsing, excess voltage and operating temperature, sometimes
requiring a careful optimization tailored for a specific application. We find
that a large flat plateau of sensitive area of about 0.5 mm in diameter, a peak
quantum efficiency of 73% at 560 nm and timing precision down to 150 ps FWHM
are the main distinguishing characteristics of this SPAD.
