HDR image sensor

Image sensors have become ubiquitous, with continuous development over the past decades perfecting the technology. State-of-the-art imagers are now approaching the theoretical limits of classical photography. However, as pixel sizes reach their physical limits, the measurable dynamic range decreases due to low pixel Full Well Capacity (FWC) and sensitivity. To address these drawbacks and further increase dynamic range, leading image sensor manufacturers are developing various pixel structures. These include techniques such as split-pixel, multiple conversion gain, LOFIC (Lateral Overflow Integration), and multiple exposure. Among these, the combination of split-pixel, multiple conversion gain, and LOFIC is widely used because it enables single-exposure imaging, minimizing image distortion. However, achieving a large size ratio between Large Pixel Photodiode (LPD) and Small Pixel Photodiode (SPD), as well as multiple conversion gain ratios within a limited area, remains challenging and requires significant space in silicon image sensors. Additionally, while silicon image sensors can detect wavelengths from visible to near infrared, many recent applications require detection up to short-wave infrared light, around 1500nm. These applications also demand extended pixel resolution and detection dynamic range, which are difficult to implement in silicon layers. Therefore, it is highly necessary to develop new pixel structures based on new materials and pixel designs for future image sensors.