Low-Noise, Radiation Tolerant SICPMs

In order to support further advances in Nuclear Physics, experiments using Cherenkov radiation and fast scintillators in calorimetry & dual calorimetry, would require new optical detectors with enhanced spectral response to blue and UV wavelengths, low timing jitter, high energy resolution, dynamic range and operation in high radiation and magnetic fields. SiPM silicon-based solid-state photo-multiplier, single-photon detector concept has turned into a valuable detector technology used in High-Energy Physics and Nuclear Physics. Silicon has though limitations as far as the UV response and radiation hardness are concerned. Silicon Carbide (SiC) is a promising semiconductor capable of UV response, lower noise, radiation hardness and operation at higher temperature. SiC has intrinsic radiation hardness superior to Si, because the energy needed to displace an atom is 2X as compared to Si. SiC's semiconductor inherent radiation hardness should enable SiCPM (Silicon Carbide PhotoMultiplier) designs with increased radiation tolerance. Short carriers paths and high velocity of the accelerated carriers in the high electric field of the Geiger avalanche photodiode pixel should allow operation with reduced sensitivity to magnetic fields as compared to PMTs and low-gain photodetectors. Due to its lower dark count rate, the SiCPM could be operated at higher over-bias above the breakdown voltage thus improving its detection efficiency and decreasing its idle power. The company has recently demonstrated for the first time the technology to fabricate through planar technology SiCPMs operated at lower voltage. The importance of this new technology resides in the capability to decrease the pixel size and increase the granularity needed in high-resolution calorimetry or tracking NP experiments. This technology is superior to the SiC MESA technology in terms of spatial resolution and, despite its infancy, SiCPMs fabricated by us through this technology have demonstrated three orders of magnitude decrease of the dark count rate as compared to MESA detectors. As the main problem with SiPMs is the excessive increase of the DCR during irradiation and require cooling to meet lifetime requirements, such initial low DCR in SiCPMs should be one of essential the factors to consider switching to SiC based single-photon detectors for operation at room temperature. Despite of intensive work on evaluating radiation damage in SiC detectors showing the superiority of the SiC semiconductor in radiation fields, no systematic investigation of SiC Geiger avalanche photodiode radiation tolerance has been carried out and there is no knowledge yet of the behavior of radiation hardness in planar SiCPMs. As damage and annealing processes are device-structure and technology-specific they could/should not be extrapolated to other structures/SiC technologies. In Phase I we propose to investigate the radiation induced damage and annealing of these SiCPM optical detectors with the goal to improve in Phase II their technology and consequently fabricate (in Phase II) detectors with increased radiation hardness. We will use the same methodology used in the past to investigate the radiation damage in SiPMs. Radiation damage in SiCPMs and test structures will be characterized after irradiation and annealing. Methods specific to Geiger operation will be adapted to the SiC material requirements.