Control of proton irradiation-induced damage in low gain avalanche detectors by heat treatment techniques

Abstract

Silicon-based particle sensors are widely employed in high-energy and nuclear physics experiments conducted at the European Organization for Nuclear Research (CERN). In recent years, silicon sensors with internal gain, known as low gain avalanche detectors (LGADs), have demonstrated an excellent performance in detecting high-energy particles owing to their good spatial and timing resolution. The sensor LGAD architecture has shown a great potential for the use in the upcoming High-Luminosity Large Hadron Collider (HL-LHC) upgrade, where semiconductor sensors will be exposed to extremely high radiation fluences. In this study, the impact of high-energy proton irradiation on the electrical performance of LGADs was investigated. The variations of critical parameters such as leakage current, effective doping concentration, carrier lifetime, spectral characteristics of radiation-induced defects, and charge collection, before and after thermal annealing at different temperatures, have been analysed using the I–V, C–V, microwave-probed photoconductivity (MW-PC), photoionization spectroscopy (PIS), and transient current (TCT) methods. It was demonstrated that the 24 GeV energy proton irradiation introduces defects, such as divacancy and trivacancy complexes, boron–oxygen and carbon–oxygen complexes, as well as divacancy–oxygen and divalent bistable defects, which act as current generation and carrier recombination centres. Annealing at temperatures of up to 400°C led to the transformation or passivation of those defects, partially restoring doping profiles and improving carrier lifetimes. These results highlight the potential of defect engineering to enhance the radiation tolerance of LGADs employed in high-energy physics applications.