Performance of large-area avalanche photodiodes at liquid nitrogen temperature

We report on the performance of beveled-edge large-area avalanche photodiodes (LAAPDs) operating at liquid nitrogen (LN/sub 2/) temperatures. The twofold purpose was to evaluate performance characteristics of LAAPD devices and feasibility of their application for scintillation light read out at LN/sub 2/ temperatures. The measurements were carried out with unpackaged 5- and 16-mm-diameter bare LAAPD devices cooled in a modified cryostat used for Si(Li) X-ray detectors. Light pulses from a green light-emitting diode and X-rays from a /sup 55/Fe source were used to characterize the performance of LAAPDs. Dark current below 1 pA was measured for a 16-mm LAAPD at a gain of 5000. The ratios of the LAAPD gain for X-rays and light pulses, the excess noise factor, and the dark noise contribution of the LAAPD preamplifier system were measured in device gain range up to 4000. Pulse-height spectra of about three photons were recorded with a 5-mm LAAPD operating at 100-K temperature and gain of 4000. A pure NaI crystal coupled to a 16-mm LAAPD was investigated, showing energy resolution of 5.9 /spl plusmn/ 0.2% for 662-keV /spl gamma/-rays from a /sup 137/Cs source.