Avalanche Photodiode-Based Active Pixel Imager

In this brief, an integrated avalanche photodiode-active pixel sensor (APD-APS) for "daylight to subtwilight" imaging has been demonstrated. Excellent logarithmic response of the APS was demonstrated by images taken with a 64 × 64 pixel array. Image degradation occurred when the APD was operated in sub-Geiger avalanche mode. Analysis of the APD current revealed that leakage from parasitic diodes obscured the internal avalanche gain. The parasitics will be shown to impede fabricating of useful APD-APS circuits and advanced isolation techniques must be employed to operate in avalanche mode.