Investigation of the Global Shutter Operation of the Quantum-Dot Short-Wave Infrared Image Sensor

Quantum dot (QD) thin-film photodiodes (TFPDs) are studied extensively in the image sensor field as they can pave the way toward the cost-efficient implementation of short-wave infrared (SWIR) cameras. Interestingly, the QD TFPD image sensors can be operated in the global shutter (GS) mode by turning on the photodiode (PD) only during integration time and subsequently turning it off during the readout. This offers the substantial advantage of reducing the pixel size as it eliminates the need for additional transistors or capacitors that are otherwise typically used in conventional GS pixels. So far, no comprehensive study has yet been performed on this PD turn on/off operation mode. Therefore, in this work, we investigated the PD turn on/off GS operation mode in comparison with the conventional voltage domain (VD) GS operation—a first in-depth report of its kind. We confirm that the PD turn on/off GS mode has the advantage of a small pixel size but comes at the cost of an increasing nonlinearity as the integration time approaches the PD speed limitation. We report a parasitic light sensitivity (PLS) of −70 dB over the visible (VIS) and SWIR range and moreover demonstrate that the PLS has the potential to reach $< -100$ dB based on the discrete PD measurement.