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The first PbS quantum dot short wave infrared imaging chip in China, which is comparable to
Time:2021-03-12 18:11:59      Click:256

Professor Tang Jiang's team from Wuhan National Research Center of Optoelectronics and School of Optics and electronic information of Huazhong University of science and technology cooperated with Hisilicon optoelectronics Co., Ltd. to prepare a photodiode with top incidence structure suitable for silicon-based readout circuit (ROIC), and realized a 300000 pixel short wave infrared chip with performance comparable to commercial indium gallium arsenic (InGaAs). It is the first lead sulfide colloidal quantum dot (PBS CQD) infrared imaging chip in China. On June 16, relevant achievements were published in the latest issue of nature electronics under the title "a near infrared colonial quantum dot imager with monolithically integrated readout circuit".

Infrared imaging chip is one of the foundations of optical sensing technology, which is widely used in machine vision, material identification, biological imaging and other emerging fields. Due to the limitation of processing temperature and single crystal substrate, the existing infrared imaging chips mainly use heterogeneous integration to realize the interconnection between infrared photodiodes and silicon-based ROIC, which faces the problems of complex process, limited resolution, large-scale production difficulties and high cost.

The monolithic integration of infrared photodiode and silicon-based ROIC has simple process and controllable cost, and is expected to greatly improve the resolution of infrared imaging chip. Unlike infrared materials grown by high-temperature epitaxy, PBS CQD is processed by low-temperature solution method, which has good substrate compatibility and can be monolithic integrated with silicon-based ROIC. However, the existing PBS CQD device structure is not suitable for silicon-based ROIC, and its depletion region is far away from the incident light, resulting in low quantum efficiency outside the device.

According to the characteristics of PBS CQD, Professor Tang Jiang's team designed a top incidence photodiode suitable for silicon-based ROIC, optimized the device structure through simulation analysis and experiments, made the depletion region close to the incident light, and realized the effective separation and collection of photogenerated carriers, so as to improve the quantum efficiency outside the device. In view of the damage of PBS CQD interface caused by high-energy particles in magnetron sputtering, the C60 interface passivation layer is introduced to reduce the interface defects. The defect concentration of the detector is reduced to 2.3 by measuring and analyzing the capacitance and capacitance voltage of the driving stage × 1016 cm − 3, close to the best value of the widely studied PBS CQD photodiode. The external quantum efficiency of the top incident PBS CQD photodiode reported in the paper is 63% and the detection rate is 2.1 × 1012 Jones, − 3dB bandwidth is 140 kHz, and the linear dynamic range is more than 100 dB.

Based on the optimal PBS CQD photodiode, the team further realized the preparation of the first PBS CQD imaging chip in China, with a resolution of 640 × 512, with a spatial resolution of 40 lp/mm (MTF50), which has an imaging effect comparable to that of commercial InGaAs imaging chips. In addition, the paper shows the application of PBS CQD infrared imaging chip in fruit detection, solvent recognition, vein imaging and so on, which proves its wide application potential.

The first author of the paper is Liu Jing, a doctoral student of Wuhan photoelectric National Research Center, and the corresponding authors are Associate Professor Gao Liang and Professor Tang Jiang. The first unit of the thesis is Huazhong University of science and technology. This research work has been strongly supported by Hisilicon optoelectronics Co., Ltd. in terms of readout circuits, as well as the facilities of the analysis and testing center of Huazhong University of science and technology and the nano characterization and device center of Wuhan optoelectronics National Research Center. This work was supported by the national key research and development plan, the National Natural Science Foundation of China, Hubei Optics Valley laboratory and the innovation fund of Wuhan optoelectronics National Research Center. At the same time, I would like to thank Professor Liu Dongsheng and Dr. Li Hao for their discussion and support in circuit.

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