We have developed heterojunction type gamma-ray detectors and neutron detectors for personal dosimeters. The former are fabricated by forming hydrogenated amorphous silicon film (a-Si:H) on high resistivity silicon substrates by using DC glow discharge in SiH4-H2 mixtures; the latter with hydrogenated amorphous10B-enriched boron film (a-B:H) on silicon substrates by that in 10B enriched B2H6-H2 mixtures. The boron film has a high concentration boron of 1×1023 atoms/cm3. The gamma-ray detector can operate at a low level of noise, 5 keV, at room temperature.
We discuss the effect of the distribution of depletion layer on the radiation detection characteristics and its application to the control of the characteristics. For gamma-ray dosimeters, it is important to optimize the surface pattern of depletion layer for the counting efficiency by effectively counting the pulse generated around the depletion region. In neutron detectors, we need to discriminate neutron rays and gamma-rays. The neutron detectors are designed to count the pulses of recoiled protons to increase the counting rate for fast neutrons without increasing the counting rate of gamma-rays. The optimum depth of the depletion layer is estimated to be 13_??_70μm in the energy range of 0.025eV-5MeV.
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