In this letter, we present a small pixel pitch image sensor optimized for high external quantum efficiency in short-wavelength infrared (SWIR). Thin-film photodiodes based on PbS colloidal quantum dot (CQD) absorber allow us to exceed the spectral limitations of silicon’s absorption while maintaining the benefits of CMOS technology. By monolithically integrating PbS CDQ thin films with CMOS readout arrays, high-pixel density SWIR image sensors can be achieved. To overcome the remaining disadvantages of the CQD-based image sensors over their bulk III-V semiconductor counterparts (lower sensitivity and reduced linearity), the thin-film photodiode stack is adapted towards the used readout circuit. A prototype image sensor with a $768\times 512$ resolution of 5- $\mu \text{m}$ pitch pixels is fabricated by using a modified 130 nm CMOS process for readout IC, together with the new CQD thin-film photodiode on top. Thanks to the optimized photodiode stack and co-integration process, the prototype image sensor shows less than 5% linearity error while having 40% external quantum efficiency in SWIR, which enables acquisition of high-quality images.

中文翻译：

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用于高性能短波长红外成像的薄膜光电探测器优化

在这封信中，我们展示了一种针对短波长红外 (SWIR) 中的高外部量子效率进行了优化的小像素间距图像传感器。基于 PbS 胶体量子点 (CQD) 吸收器的薄膜光电二极管使我们能够超越硅吸收的光谱限制，同时保持 CMOS 技术的优势。通过将 PbS CDQ 薄膜与 CMOS 读出阵列单片集成，可以实现高像素密度的 SWIR 图像传感器。为了克服基于 CQD 的图像传感器相对于其体 III-V 半导体同类产品的剩余缺点（较低的灵敏度和较低的线性度），薄膜光电二极管堆栈适用于所使用的读出电路。原型图像传感器 768 美元\乘以 512 美元 分辨率为 5- $\mu \text{m}$ 间距像素是通过使用改进的 130 nm CMOS 工艺制造出来的，用于读出 IC，以及顶部的新型 CQD 薄膜光电二极管。得益于优化的光电二极管堆栈和协集成工艺，原型图像传感器显示出小于 5% 的线性误差，同时在 SWIR 中具有 40% 的外部量子效率，从而能够获取高质量的图像。