| Detection, like "eye", it is an indispensable important technical means to explore and reveal the unknown field for human. In numerous detectors, the semiconductor detectors has become an important carrier for optical signal detection, due to their advantages in terms of small volume, light weight, shock resistant, high efficiency, low power consumption, long life, wide spectrum, etc. Semiconductor detectors are not only a necessary part of semiconductor optoelectronics, but also a crucial role in the military, defense, deep space exploration, scientific research, medical treatment, optical communication, etc. Semiconductor detectors, as a high and new technology, are to grab the commanding heights of the various countries.Silicon photodetector is the powerful force for the visible light and near infrared band detectors. It has been widely used in aerospace, security, health care, intelligent control and other fields, because the high efficiency, low power consumption, small volume, shock resistant, and so on. However, silicon photodetector in our country are mainly rely on import, which not only lead to its price accounts for a third to a half for the entire device, but also gotten international blockade in high-end devices, so it is necessary to independent to carry out the research of silicon photodetectors.In this dissertation, researches are focused on high quantum efficiency of silicon PIN photodetector based on the basic theory of semiconductor physics. This paper uses the carrier collection enhanced structure in silicon PIN photodetector, and studies the important factors which effective the quantum efficiency and dark current. The multilayer antireflection coatings(AR coatings) structure is optimized by the ant colony algorithm(ACA) theory at normal incident and the omnidirectional incident of broadband spectrum. On the experimental aspect, we fabricated the silicon PIN photodiode with the carrier collection enhanced structure, which was the same type and comparable performance compared with Japanese Hamamatsu devices. The researches can be summarized as follows:Firstly, we propose a cross finger structure for enhancing the carrier collection, base on the further physical analysis of the photodetector and the relationship among the quantum efficiency, dark current and capacitance with structure of photodetector. The silicon PIN photodetector contrals the carriers by the transverse electric field in active area, and then improves the collection efficiency of carrier, reduces the carrier surface recombination and finally increases the quantum efficiency.Then, the device structure and the fabricated processing are optimized, include the distance between the fingers, ion implant and annealing process. The performances of silicon PIN photodetector with cross finger structure are equal to even more beyond the device of Hamamatsu. The performances in the experimental are shown below: the dark current at-10 mV of silicon PIN photodetector is only 1.3pA, smaller than 4pA of Hamamatsu S5668; the quantum efficiency of silicon PIN photodetector is higher than Hamamatsu S5668 over 300nm- 1100 nm. The sample of silicon PIN photodetector with cross finger structure is verified in NUCTECH’s X-ray screening system, and receives recognition from a number of companies for the excellent performance.Finally, we present the designed method based on the ACA to optimize the broadband omnidirectional AR coatings. Compaerd to the genetic algorithm and simulated annealing algorithm, the highest transmittance is reached by ACA over 0-90 incident angle range and 300nm-1100 nm wavelength range. This result shown the superiority of ACA in AR coatings optimized. In order to improve the adaptability of the AR coatings optimized by ACA, the solar spectrum is incorporated into ACA which change with the latitude. The solar spectrums in Quito, Beijing and Moscow with different latitude are used as examples, the optimized incident efficiencys are increased by 0.26%, 1.37% and 4.24%, when the solar cells placed horizontally.
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