Ultrafast Solid State Detectors for 4D Tracking in High Energy Physics and Medical Applications

Abstract

Silicon-Carbide (SiC) detectors are used at the forefront of particle detector research because of their large band gap of 3.36eV, their radiation hardness, large critical electric field, high mobility,and the ability to be operated without cooling due to their low leakage current. Furthermore, the 4H-SiC polytpe, the most commonly used polytype of SiC, exhibits additional properties, such as an increased charge-carrier saturation drift velocity, an increased atomic displacement threshold energy, higher thermal conductivity and lower leakage currents after irradiation. This makes 4H-SiC detectors ideally suited for precise time measurements in high-radiation environments, such as high-energy particle physics and radiation therapy treatments. As particle accelerator collision experiments continuously aim for higher luminosities, particle detectors which provide not only a precise spatial resolution but also a precise time resolution (4D-Tracking) become essential in distinguishing individual particle-particle interactions during pile-up events. Alternatively, 4H-SiC detectors can be utilized in medical accelerator facilities for ion computed tomography (iCT), an ion based imaging method to determine the relative stopping power (RSP) distribution within the patient. Here ultra-fast 4D-Tracking detectors can be utilized to precisely determine the path of the particles and the energy loss through the tissue using time-of-flight (TOF) measurements to infer the RSP from the residual energy of the particles, with novel methods even combining 4D-tracking and TOF measurements into one framework using SiC-LGADs. Advances in iCT could translate into improved treatment planning for ion radiation therapy treatments. The aim of this thesis is to investigate and probe time resolution limits of 4H-SiC detectors using the transient current technique (TCT), where the signal generated by the drift of electron-hole pairs within the detector created via an ultraviolet laser is analyzed. In particular, how does the time resolution of these detectors behave in the low minimum ionizing particle (MIP) regime and what are the limiting factors of the detectors and measurement electronics used. First, a theoretical background will be provided in which the underlying physical interactions at play and the detector properties are discussed, followed by the electrical characterization of the said detectors. Afterwards, the TCT measurement data will be presented and analyzed. Lastly, the results, as well as an outlook on possible future research, will be discussed.