Hot carriers effects and electroluminescence in the CMOS photodiode active pixel sensors

摘要

In this paper, we demonstrate that an electroluminescence phenomenon associated to hot carriers generation of the in-pixel source follower transistor can occur in CMOS APS pixels. These effects have been observed in several process generations ranging from 0.7μm to 0.25μm with various power supply voltage values. This paper is focused mainly on the behavior of 0.5μm and 0.25μm generation. It is shown that when a pixel is selected its follower transistor can generate excess minority carriers, and that a small amount of these charges flows towards the photosensitive area to be collected. This implies a significant drop of the photodiode voltage when the amount of the collected carriers becomes larger than the junction leakage current.