Silicon semiconductor detectors for various nuclear radiations

Silicon semiconductor detectors for a nuclear radiation monitor of various rays (γ rays, neutrons and charged particles) have been developed. These detectors are diffused p-n junction type devices with low leakage current. The γ ray detector is produced, using high resistivity p-type silicon (2-10 k Ω·cm), to increase thickness of the depletion layer. This detector has been applied as an area monitor and a computerized personal dosimeter with an IC card. For the neutron detector, proton radiators and boron convertors are coated on the surface of the detector element. Neutrons are detected as recoil protons by interaction of the proton radiator and, as α-particles generated by the nuclear reaction ¹⁰B(n,α)⁷Li. The energy response of this detector meets the ICRP recommendation for a radiation monitor. The charged particles (α, β rays) detector having a large sensitive area (up to 6000 mm³) is coated with double passivation layers (Si₃N₄/SiO₂) on the surface of the detector element in order to reduce leakage current due to surface stress. The leakage current of less than 220 nA is achieved for the sensitive area by application of the double layers. The charged particles detector can be applied as a radioactive dust monitor and a contamination monitor, and the neutron detector is suited as an area monitor and a personal dosimeter