AC-LGAD silicon detectors with alternate gain layer for improved reliability

C55-22c-270318More stringent challenges, as required by future high energy physics experiments, require higher radiation tolerance and higher granularity to the silicon detectors. Recently developed precision timing detector technology based on silicon Low Gain Avalanche Diode (LGAD) although exhibits excellent timing performance, cannot attain 10 µm position resolution needed for advanced 4D detectors. Also, owing to the shallow implant design of the gain layer, the radiation tolerance of LGADs is limited. Gain layer design with tolerance to higher irradiation fluences as well as detector design that allows shrinking the pixel pitch is desired for future detector upgrades. Optimization of the buried junction design with considerations to dopant layer depth and width by modeling AC coupled LGAD (AC-LGAD) device geometry using Technology Computer Aided Design (TCAD). Effectiveness of deep trench as junction termination edge (JTE) will also be validated for improved breakdown reliability. Modeling efforts will be complemented by experimental methods to develop buried junction layers with in-situ doping strategies of epitaxial silicon layers. The Phase I effort is aimed at developing TCAD models to determine optimum position, doping levels and JTE of the buried junction sensor design in order to improve the overall gain, radiation hardness and breakdown reliability of the detector in AC-LGAD geometry. Concurrently, experimental methods will be developed to achieve buried junction at variable depths by exploring epitaxial growth of silicon. In-situ doping will be explored to achieve tunable and hyper abrupt gain layer profile. Deep trench geometries will be explored for junction terminations. Secondary Ion Mass Spectroscopy (SIMS) depth profiling will be used to map depth and dopant concentration to validate the grown films. Radiation hard, high granularity detectors will find immediate application in detector chips to be used in MIP Timing Detector to be deployed as part of the CMS Upgrade at CERN as well as newly conceived advanced Electron-Ion Collider (EIC) for precision timing and position application. Longer term applications include full vertically integrated highly segmented, high-density detectors for nuclear particle detectors, and a wide variety of medical imaging applications such as Clinical dosimetry, Positron Emission Tomography (PET) to name a few.