Comparing leakage currents and dark count rates in Geiger-mode avalanche photodiodes

This letter presents an experimental study of dark count rates and leakage current in Geiger-mode avalanche photodiodes (GM APD). Experimental results from circular diodes over a range of areas (20-500 μm diam), exhibit leakage current levels orders of magnitude higher than anticipated from dark count rates. Measurements of the area and peripheral components of the leakage current indicate that the majority of the current in reverse bias does not enter the high-field region of the diode, and therefore, does not contribute to the dark count rate. Extraction of the area leakage current term from large-area devices (500 μm) corresponds well with the measured dark count rates on smaller devices (20 μm). Finally, the work indicates how dark count measurements represent 10^-18A levels of leakage current detection in GM APDs.