Planar silicon PIN diodes have been proposed as neutron dosimeters before. In this paper, a new structure of planar silicon PIN diode with ring shaped backside n + doping is proposed. Simulation shows effective improvement in the current distribution compared with a normal planar PIN structure. Diodes with different lateral spaces between p + and n + , i.e., 200-500 µm, were fabricated. The sensitivity of the diodes to neutron irradiation was measured. The dependence of the sensitivity on the working current of the diode was analyzed. The impact of the lateral space on the diode sensitivity was investigated. The results show that the sensitivity of the diode is proportional to the square root of the current at high-level injection and increases with the lateral space between the p + and n + regions.

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Two batches of diodes, with different structural ratios (the ratio of area and thickness), were made using different manufacturing processes. The energy response of the first batch to 15 kinds of monoenergetic neutrons ranging from 180 keV to 17.56 MeV was tested, and the neutron source response of both batches to 239Pu-Be neutron source was measured. The energy deposition in the diodes irradiated by 1 keV to 20 MeV monoenergetic neutrons was calculated with simulation procedure. The response curve of the experimental results showed an approximately similar trend to that of theoretical computation. Based on the results of the neutron source response experiments, it was concluded that the response of fast neutron varied linearly with the structural ratio of the detectors.

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