As the rapid development of back-illuminated CMOS (BI-CMOS) image sensor technology in recent years, its application prospect in the field of Low-Light-Level (LLL) night vision has been widely concerned. Therefore, LLL imaging module was developed based on BICMOS, whose 3-D noise data was obtained under different illumination conditions. The test results show that, the signal-to-noise ratio (SNR) of imaging module becomes worse with the decreasing of illumination. According to the judgement of noise, the noise power of the image in low illumination is mainly Gaussian distribution. And the image processed by spatial filtering, which efficiently reducing the imaging noise and improving the imaging quality.
The flawed surface of GaAs/GaAlAs heterointerface after wet etching by H<sub>2</sub>O<sub>2</sub> and NH<sub>4</sub>OH based etch ant was studied in this work. The results showed that the surface of GaAs/GaAlAs heterointerface had convex point, etching pits, pinhole, fog point, and friction scratches were investigated with a etch step measurement. And imprinting the main reasons for the formation of the etching surface defects of GaAs/GaAlAs are the poor quality of epitaxial materials, the contamination of materials surface, the unclear interface of oxidation and doping, the inhomogeneity of concentration and the operation errors. The selective etching of the GaAs/GaAlAs material eliminates some flaws and improves the quality of the etching surface of the GaAs/GaAlAs material.