Intercomparison IC2021area of passive area dosimetry systems

The EURADOS intercomparison IC2021area was carried out between May 2021 and April 2022 for 66 participating passive H*(10) area dosimetry systems from 47 different institutes and monitoring services. Three measurement conditions were provided at locations of the Karlsruhe Institute of Technology: 3-months indoor, 3-months outdoor and 6-months outdoor. The challenge of this intercomparison was measuring additionally irradiated low dose radiation. Six dosemeters of each participating system were irradiated with Cs-137 gamma reference radiation: Three dosemeters with 150 µSv and three dosemeters with 300 µSv. Another six dosemeters of each participating system were not irradiated and were used for background dose subtraction. Typical values of the measured background dose were between 200 µSv and 450 µSv with a few significantly higher values up to 1.6 mSv. Despite the challenge of the low reference dose values, more than 90 % of the resulting response values of the irradiated dosemeters were within the recommended ISO 14146 trumpet curve response limits.Peer ReviewedPostprint (published version

Low dose response results and detection limits of the EURADOS intercomparison IC2021area for passive H*(10) area dosemeters

The EURADOS intercomparison IC2021area with its main focus on low dose measurements was carried out between May 2021 and April 2022 for passive H*(10) area dosimetry systems. Three measurement conditions were provided at locations of the Karlsruhe Institute of Technology: 3-months indoor, 3-months outdoor and 6-months outdoor. The challenge for the 65 participating dosimetry systems of this intercomparison was measuring additionally irradiated low dose 137Cs gamma radiation of 150 µSv and 300 µSv. Despite the comparably high background dose values between about 200 µSv and 1600 µSv, more than 90% of the resulting response values of the irradiated dosemeters were within the recommended ISO 14146 response limits. The calculated detection limits of the participating dosimetry systems were in most cases clearly below the desired value of 150 µSv of this intercomparison.Peer ReviewedPostprint (published version

Reverse breakdown and light-emission patterns studied in Si PureB SPADs

The relationship between light-emission patterns from silicon avalanche-mode light-emitting diodes (AMLEDs), and avalanche breakdown was investigated using photodiodes fabricated in pure boron (PureB) technology. The quality of the diodes ranged from high-quality, low dark-current devices with abrupt breakdown characteristics that were suitable for operation as single-photon avalanche diodes (SPADs), to diodes with gradually increasing reverse currents before actual breakdown. The reverse I-V characteristics were measured and correlated to light-emission data obtained simultaneously using a PureB photodetector, and inspected using a camera with which distinct emission patterns could be identified. When increasing the voltage far past breakdown, light emission invariably becomes dominant at the photodiode periphery. Based on the examination of a large variety of anode geometries, it is concluded that the most efficient light emission per consumed power is achieved with defect-free narrow-anode diodes that also are applicable as low-dark-count-rate SPADs

Impact of ultra-thin-layer material parameters on the suppression of carrier injection in rectifying junctions formed by interfacial charge layers

Pure amorphous boron (PureB) deposition on Si is used to fabricate ultrashallow low-saturation-current p+n-like diodes even at process temperatures where the boron is not expected to diffuse into the bulk Si. It has been proposed that the bonding of the B atoms to the Si creates a monolayer of fixed negative charge that attracts holes to the interface. In this paper, an investigation using semiconductor simulation tools is performed starting from an all-Si test structure where suppression of electron injection from an n-Si bulk was achieved by introducing a large concentration of negative fixed charge that attracts holes to the interface between a thin-film top-layer and the bulk. This introduces a barrier which lowers the electron saturation current density of the simulated diode to become comparable to or lower than the saturation current density of holes injected into the bulk. The material properties of the top-layer such as electron mobility and tunneling mass, bandgap and electron affinity are individually varied from default Si-values to values typical for amorphous boron layers indicating that a critical concentration of negative fixed charge is always needed for suppression of the electron injection