Research Projects

• Background and Motivation: Silicon-based radiation detectors are indispensable in high-energy physics experiments, medical imaging modalities like Time-of-Flight Positron Emission Tomography (TOF-PET), and space instrumentation. Conventional PIN diodes, avalanche photodiodes, and SiPMs each have trade-offs among gain, noise, timing resolution, and fill factor. Low-Gain Avalanche Detectors (LGADs) represent a new class of silicon devices that achieve moderate internal gain (~5–20×) while delivering sub-50 picosecond timing resolution and high radiation tolerance ([Pellegrini 2014], Sadrozinski 2018]). • Hypothesis: We hypothesize that it is feasible to design and fabricate LGAD detectors domestically using Indian semiconductor facilities, achieving time resolution ≤50 ps, gain in the 5–20× range, and leakage currents 10 nA/cm² or less — performance comparable to internationally produced devices. • Objectives: (1) Develop optimized LGAD architectures compatible with high-resistivity silicon substrates and existing domestic semiconductor fabrication processes. (2) Simulate electrical characteristics and timing response using TCAD and WeightField2. (3) Fabricate pilot LGAD batches. (4) Characterize device performance before and after radiation exposure. (5) Establish protocols and infrastructure to serve as the foundation for future AC-LGAD and monolithic CMOS pixel detectors. • Expected Impact: This will be India’s first comprehensive program to design, fabricate, and validate LGAD devices, enabling advanced detector capabilities for scientific, medical, and strategic applications • Quantitate KPIs: (1) Time Resolution (single hit): 50 ps or less (2) Gain: 5–20× uniform across 70% or more of active area (3) Leakage Current: 10 nA/cm2 or less (4) Breakdown Voltage: 400 V or more (5) Radiation Tolerance: 1 MGy (gamma dose) or more • Justification of KPIs for Applications: {1} Time-of-Flight PET Imaging: - Timing resolution determines spatial uncertainty: Δx = c × Δt / 2. Current TOF-PET systems have ~200–400 ps timing (3–6 cm uncertainty). Achieving 50 ps reduces uncertainty to ~0.75 cm, improving image resolution by ~4× and enabling up to 2× lower radiation dose ([Conti 2009], [Surti 2007]). {2} Space Applications: - Standard PIN diodes degrade above ~100 kGy, limiting life to ~2 years. LGADs with 1 MGy tolerance extend life to ~10 years and maintain timing performance ([Kramberger 2015], [ESA 2014]). • References: 1. Pellegrini et al., NIM A, 2014. 2. Sadrozinski et al., Rep Prog Phys, 2018. 3. Conti, Phys Med, 2009. 4. Surti et al., J Nucl Med, 2007. 5. Kramberger et al., JINST, 2015. 6. ESA Radiation Effects, 2014.