Nuclear radiation detectors using thick amorphous-silicon MIS devices

Metal insulator semiconductor (MIS) devices made from hydrogenated amorphous silicon (a-Si:H) were developed for the detection of charged particles. Devices with a Cr/a-SiN_x:H/a-Si:H structure and with varying thicknesses from 3 to 20 μm (a-Si:H layer) were fabricated using the radio-frequency plasma enhanced chemical vapour deposition (PECVD) technique. They were used for the detection of alpha particles (E = 5.5 MeV, ²⁴¹Am source) and low-energy beta particles (E<; 156 keV, ¹⁴C). The characteristics of the MIS detectors were compared to that of PIN diodes made using the same PECVD apparatus and processes. MIS detectors appeared to be well suited for the detection of charged particles, with better properties than that of PIN diodes for low-energy alpha particle detection (E<; 2 MeV). MIS devices were shown to be a very interesting alternative to the commonly used PIN diodes, as they rely on a more straightforward fabrication process and setup, that in particular avoids the use of hazardous doping gases such as phosphine.